Vulnerability-Lookup

CVE-2026-18401 (GCVE-0-2026-18401)

Vulnerability from cvelistv5 – Published: 2026-08-04 14:23 – Updated: 2026-08-04 17:59 X_Open Source

Title

jackson-core: Number length constraint bypass in non-blocking (async) JSON parser leads to potential denial of service

Summary

The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service. No privileges or user interaction beyond the ability to submit data for parsing are required. This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x. Versions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

HeroDevs

References

3 references

URL	Tags
https://github.com/FasterXML/jackson-core/securit…	vendor-advisory
https://github.com/FasterXML/jackson-core/pull/1555	patch
https://github.com/FasterXML/jackson-core/commit/…	patch

Impacted products

2 products

Vendor	Product	Version
FasterXML	jackson-core	Affected: 2.15.0 , ≤ 2.18.5 (maven) Unaffected: 2.18.6 (maven) Affected: 2.19.0 , < 2.21.1 (maven) Unaffected: 2.21.1 (maven)
FasterXML	jackson-core	Affected: 3.0.0 , < 3.1.0 (maven) Unaffected: 3.1.0 (maven)

Credits

sprabhav7 rohan-repos neilmadden-hazelcast awsactran pjfanning (PJ Fanning) cowtowncoder (Tatu Saloranta)

Show details on NVD website

JSON

To clipboard

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\"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"LOW\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"Application parses attacker-supplied JSON using the non-blocking parser API, for example JsonFactory.createNonBlockingByteArrayParser() in a Spring WebFlux or other reactive service.\"}]}], \"affected\": [{\"repo\": \"https://github.com/FasterXML/jackson-core\", \"vendor\": \"FasterXML\", \"product\": \"jackson-core\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.15.0\", \"versionType\": \"maven\", \"lessThanOrEqual\": \"2.18.5\"}, {\"status\": \"unaffected\", \"version\": \"2.18.6\", \"versionType\": \"maven\"}, {\"status\": \"affected\", \"version\": \"2.19.0\", \"lessThan\": \"2.21.1\", \"versionType\": \"maven\"}, {\"status\": \"unaffected\", \"version\": \"2.21.1\", \"versionType\": \"maven\"}], \"packageName\": \"com.fasterxml.jackson.core:jackson-core\", \"programFiles\": [\"src/main/java/com/fasterxml/jackson/core/json/async/NonBlockingUtf8JsonParserBase.java\"], \"collectionURL\": \"https://repo.maven.apache.org/maven2\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"NonBlockingUtf8JsonParserBase._finishNumberIntegralPart\"}, {\"name\": \"NonBlockingUtf8JsonParserBase._valueComplete\"}]}, {\"repo\": \"https://github.com/FasterXML/jackson-core\", \"vendor\": \"FasterXML\", \"product\": \"jackson-core\", \"versions\": [{\"status\": \"affected\", \"version\": \"3.0.0\", \"lessThan\": \"3.1.0\", \"versionType\": \"maven\"}, {\"status\": \"unaffected\", \"version\": \"3.1.0\", \"versionType\": \"maven\"}], \"packageName\": \"tools.jackson.core:jackson-core\", \"programFiles\": [\"src/main/java/tools/jackson/core/json/async/NonBlockingUtf8JsonParserBase.java\"], \"collectionURL\": \"https://repo.maven.apache.org/maven2\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"NonBlockingUtf8JsonParserBase._finishNumberIntegralPart\"}, {\"name\": \"NonBlockingUtf8JsonParserBase._valueComplete\"}]}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2026-02-22T20:17:00.000Z\", \"value\": \"Fix merged upstream via FasterXML/jackson-core#1555 (milestone 2.18.6)\"}, {\"lang\": \"en\", \"time\": \"2026-02-26T00:00:00.000Z\", \"value\": \"GHSA-72hv-8253-57qq published by the maintainer in FasterXML/jackson-core\"}, {\"lang\": \"en\", \"time\": \"2026-02-28T00:00:00.000Z\", \"value\": \"Advisory reviewed and published to the GitHub Advisory Database\"}], \"references\": [{\"url\": \"https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq\", \"name\": \"GHSA-72hv-8253-57qq\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://github.com/FasterXML/jackson-core/pull/1555\", \"name\": \"FasterXML/jackson-core#1555\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/FasterXML/jackson-core/commit/b0c428e6f993e1b5ece5c1c3cb2523e887cd52cf\", \"name\": \"FasterXML/jackson-core@b0c428e\", \"tags\": [\"patch\"]}], \"x_generator\": {\"engine\": \"Vulnogram 0.5.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service.\\n\\n\\n\\nThe synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.\\n\\n\\n\\nRoot cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.\\n\\n\\n\\nImpact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service.\\n\\n\\n\\nNo privileges or user interaction beyond the ability to submit data for parsing are required.\\n\\n\\n\\nThis issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x.\\n\\n\\n\\nVersions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eThe non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service.\u003c/p\u003e\u003cp\u003eThe synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.\u003c/p\u003e\u003cp\u003e\u003cb\u003eRoot cause:\u003c/b\u003e the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.\u003c/p\u003e\u003cp\u003e\u003cb\u003eImpact:\u003c/b\u003e an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service.\u003c/p\u003e\u003cp\u003eNo privileges or user interaction beyond the ability to submit data for parsing are required.\u003c/p\u003e\u003cp\u003eThis issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x.\u003c/p\u003e\u003cp\u003eVersions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-770\", \"description\": \"CWE-770 Allocation of Resources Without Limits or Throttling\"}]}], \"providerMetadata\": {\"orgId\": \"36c7be3b-2937-45df-85ea-ca7133ea542c\", \"shortName\": \"HeroDevs\", \"dateUpdated\": \"2026-08-04T14:23:27.174Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-18401\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-04T17:59:07.408Z\", \"dateReserved\": \"2026-07-30T15:20:53.701Z\", \"assignerOrgId\": \"36c7be3b-2937-45df-85ea-ca7133ea542c\", \"datePublished\": \"2026-08-04T14:23:27.174Z\", \"assignerShortName\": \"HeroDevs\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

GHSA-6QM2-MCQ7-53QP

Vulnerability from github – Published: 2026-08-04 15:32 – Updated: 2026-08-04 15:32

Details

The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.

Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.

Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service.

No privileges or user interaction beyond the ability to submit data for parsing are required.

This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x.

Versions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-18401"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-04T15:16:29Z",
    "severity": "MODERATE"
  },
  "details": "The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service.\n\n\n\nThe synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.\n\n\n\nRoot cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.\n\n\n\nImpact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service.\n\n\n\nNo privileges or user interaction beyond the ability to submit data for parsing are required.\n\n\n\nThis issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x.\n\n\n\nVersions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.",
  "id": "GHSA-6qm2-mcq7-53qp",
  "modified": "2026-08-04T15:32:23Z",
  "published": "2026-08-04T15:32:23Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-18401"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-core/pull/1555"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-core/commit/b0c428e6f993e1b5ece5c1c3cb2523e887cd52cf"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

GHSA-72HV-8253-57QQ

Vulnerability from github – Published: 2026-02-28 02:01 – Updated: 2026-08-03 20:32

Summary

jackson-core: Number Length Constraint Bypass in Async Parser Leads to Potential DoS Condition

Details

Summary

The non-blocking (async) JSON parser in jackson-core bypasses the maxNumberLength constraint (default: 1000 characters) defined in StreamReadConstraints. This allows an attacker to send JSON with arbitrarily long numbers through the async parser API, leading to excessive memory allocation and potential CPU exhaustion, resulting in a Denial of Service (DoS).

The standard synchronous parser correctly enforces this limit, but the async parser fails to do so, creating an inconsistent enforcement policy.

Details

The root cause is that the async parsing path in NonBlockingUtf8JsonParserBase (and related classes) does not call the methods responsible for number length validation.

The number parsing methods (e.g., _finishNumberIntegralPart) accumulate digits into the TextBuffer without any length checks.
After parsing, they call _valueComplete(), which finalizes the token but does not call resetInt() or resetFloat().
The resetInt()/resetFloat() methods in ParserBase are where the validateIntegerLength() and validateFPLength() checks are performed.
Because this validation step is skipped, the maxNumberLength constraint is never enforced in the async code path.

PoC

The following JUnit 5 test demonstrates the vulnerability. It shows that the async parser accepts a 5,000-digit number, whereas the limit should be 1,000.

package tools.jackson.core.unittest.dos;

import java.nio.charset.StandardCharsets;

import org.junit.jupiter.api.Test;

import tools.jackson.core.*;
import tools.jackson.core.exc.StreamConstraintsException;
import tools.jackson.core.json.JsonFactory;
import tools.jackson.core.json.async.NonBlockingByteArrayJsonParser;

import static org.junit.jupiter.api.Assertions.*;

/**
 * POC: Number Length Constraint Bypass in Non-Blocking (Async) JSON Parsers
 *
 * Authors: sprabhav7, rohan-repos
 * 
 * maxNumberLength default = 1000 characters (digits).
 * A number with more than 1000 digits should be rejected by any parser.
 *
 * BUG: The async parser never calls resetInt()/resetFloat() which is where
 * validateIntegerLength()/validateFPLength() lives. Instead it calls
 * _valueComplete() which skips all number length validation.
 *
 * CWE-770: Allocation of Resources Without Limits or Throttling
 */
class AsyncParserNumberLengthBypassTest {

    private static final int MAX_NUMBER_LENGTH = 1000;
    private static final int TEST_NUMBER_LENGTH = 5000;

    private final JsonFactory factory = new JsonFactory();

    // CONTROL: Sync parser correctly rejects a number exceeding maxNumberLength
    @Test
    void syncParserRejectsLongNumber() throws Exception {
        byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);

        // Output to console
        System.out.println("[SYNC] Parsing " + TEST_NUMBER_LENGTH + "-digit number (limit: " + MAX_NUMBER_LENGTH + ")");
        try {
            try (JsonParser p = factory.createParser(ObjectReadContext.empty(), payload)) {
                while (p.nextToken() != null) {
                    if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {
                        System.out.println("[SYNC] Accepted number with " + p.getText().length() + " digits — UNEXPECTED");
                    }
                }
            }
            fail("Sync parser must reject a " + TEST_NUMBER_LENGTH + "-digit number");
        } catch (StreamConstraintsException e) {
            System.out.println("[SYNC] Rejected with StreamConstraintsException: " + e.getMessage());
        }
    }

    // VULNERABILITY: Async parser accepts the SAME number that sync rejects
    @Test
    void asyncParserAcceptsLongNumber() throws Exception {
        byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);

        NonBlockingByteArrayJsonParser p =
            (NonBlockingByteArrayJsonParser) factory.createNonBlockingByteArrayParser(ObjectReadContext.empty());
        p.feedInput(payload, 0, payload.length);
        p.endOfInput();

        boolean foundNumber = false;
        try {
            while (p.nextToken() != null) {
                if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {
                    foundNumber = true;
                    String numberText = p.getText();
                    assertEquals(TEST_NUMBER_LENGTH, numberText.length(),
                        "Async parser silently accepted all " + TEST_NUMBER_LENGTH + " digits");
                }
            }
            // Output to console
            System.out.println("[ASYNC INT] Accepted number with " + TEST_NUMBER_LENGTH + " digits — BUG CONFIRMED");
            assertTrue(foundNumber, "Parser should have produced a VALUE_NUMBER_INT token");
        } catch (StreamConstraintsException e) {
            fail("Bug is fixed — async parser now correctly rejects long numbers: " + e.getMessage());
        }
        p.close();
    }

    private byte[] buildPayloadWithLongInteger(int numDigits) {
        StringBuilder sb = new StringBuilder(numDigits + 10);
        sb.append("{\"v\":");
        for (int i = 0; i < numDigits; i++) {
            sb.append((char) ('1' + (i % 9)));
        }
        sb.append('}');
        return sb.toString().getBytes(StandardCharsets.UTF_8);
    }
}

Impact

A malicious actor can send a JSON document with an arbitrarily long number to an application using the async parser (e.g., in a Spring WebFlux or other reactive application). This can cause: 1. Memory Exhaustion: Unbounded allocation of memory in the TextBuffer to store the number's digits, leading to an OutOfMemoryError. 2. CPU Exhaustion: If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM can be tied up in O(n^2) BigInteger parsing operations, leading to a CPU-based DoS.

Suggested Remediation

The async parsing path should be updated to respect the maxNumberLength constraint. The simplest fix appears to ensure that _valueComplete() or a similar method in the async path calls the appropriate validation methods (resetInt() or resetFloat()) already present in ParserBase, mirroring the behavior of the synchronous parsers.

NOTE: This research was performed in collaboration with rohan-repos

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "tools.jackson.core:jackson-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.19.0"
            },
            {
              "fixed": "2.21.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.18.5"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.15.0"
            },
            {
              "fixed": "2.18.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-28T02:01:05Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\nThe non-blocking (async) JSON parser in `jackson-core` bypasses the `maxNumberLength` constraint (default: 1000 characters) defined in `StreamReadConstraints`. This allows an attacker to send JSON with arbitrarily long numbers through the async parser API, leading to excessive memory allocation and potential CPU exhaustion, resulting in a Denial of Service (DoS).\n\nThe standard synchronous parser correctly enforces this limit, but the async parser fails to do so, creating an inconsistent enforcement policy.\n\n### Details\nThe root cause is that the async parsing path in `NonBlockingUtf8JsonParserBase` (and related classes) does not call the methods responsible for number length validation.\n\n- The number parsing methods (e.g., `_finishNumberIntegralPart`) accumulate digits into the `TextBuffer` without any length checks.\n- After parsing, they call `_valueComplete()`, which finalizes the token but does **not** call `resetInt()` or `resetFloat()`.\n- The `resetInt()`/`resetFloat()` methods in `ParserBase` are where the `validateIntegerLength()` and `validateFPLength()` checks are performed.\n- Because this validation step is skipped, the `maxNumberLength` constraint is never enforced in the async code path.\n\n### PoC\nThe following JUnit 5 test demonstrates the vulnerability. It shows that the async parser accepts a 5,000-digit number, whereas the limit should be 1,000.\n\n```java\npackage tools.jackson.core.unittest.dos;\n\nimport java.nio.charset.StandardCharsets;\n\nimport org.junit.jupiter.api.Test;\n\nimport tools.jackson.core.*;\nimport tools.jackson.core.exc.StreamConstraintsException;\nimport tools.jackson.core.json.JsonFactory;\nimport tools.jackson.core.json.async.NonBlockingByteArrayJsonParser;\n\nimport static org.junit.jupiter.api.Assertions.*;\n\n/**\n * POC: Number Length Constraint Bypass in Non-Blocking (Async) JSON Parsers\n *\n * Authors: sprabhav7, rohan-repos\n * \n * maxNumberLength default = 1000 characters (digits).\n * A number with more than 1000 digits should be rejected by any parser.\n *\n * BUG: The async parser never calls resetInt()/resetFloat() which is where\n * validateIntegerLength()/validateFPLength() lives. Instead it calls\n * _valueComplete() which skips all number length validation.\n *\n * CWE-770: Allocation of Resources Without Limits or Throttling\n */\nclass AsyncParserNumberLengthBypassTest {\n\n    private static final int MAX_NUMBER_LENGTH = 1000;\n    private static final int TEST_NUMBER_LENGTH = 5000;\n\n    private final JsonFactory factory = new JsonFactory();\n\n    // CONTROL: Sync parser correctly rejects a number exceeding maxNumberLength\n    @Test\n    void syncParserRejectsLongNumber() throws Exception {\n        byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);\n\t\t\n\t\t// Output to console\n        System.out.println(\"[SYNC] Parsing \" + TEST_NUMBER_LENGTH + \"-digit number (limit: \" + MAX_NUMBER_LENGTH + \")\");\n        try {\n            try (JsonParser p = factory.createParser(ObjectReadContext.empty(), payload)) {\n                while (p.nextToken() != null) {\n                    if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {\n                        System.out.println(\"[SYNC] Accepted number with \" + p.getText().length() + \" digits \u2014 UNEXPECTED\");\n                    }\n                }\n            }\n            fail(\"Sync parser must reject a \" + TEST_NUMBER_LENGTH + \"-digit number\");\n        } catch (StreamConstraintsException e) {\n            System.out.println(\"[SYNC] Rejected with StreamConstraintsException: \" + e.getMessage());\n        }\n    }\n\n    // VULNERABILITY: Async parser accepts the SAME number that sync rejects\n    @Test\n    void asyncParserAcceptsLongNumber() throws Exception {\n        byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);\n\n        NonBlockingByteArrayJsonParser p =\n            (NonBlockingByteArrayJsonParser) factory.createNonBlockingByteArrayParser(ObjectReadContext.empty());\n        p.feedInput(payload, 0, payload.length);\n        p.endOfInput();\n\n        boolean foundNumber = false;\n        try {\n            while (p.nextToken() != null) {\n                if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {\n                    foundNumber = true;\n                    String numberText = p.getText();\n                    assertEquals(TEST_NUMBER_LENGTH, numberText.length(),\n                        \"Async parser silently accepted all \" + TEST_NUMBER_LENGTH + \" digits\");\n                }\n            }\n            // Output to console\n            System.out.println(\"[ASYNC INT] Accepted number with \" + TEST_NUMBER_LENGTH + \" digits \u2014 BUG CONFIRMED\");\n            assertTrue(foundNumber, \"Parser should have produced a VALUE_NUMBER_INT token\");\n        } catch (StreamConstraintsException e) {\n            fail(\"Bug is fixed \u2014 async parser now correctly rejects long numbers: \" + e.getMessage());\n        }\n        p.close();\n    }\n\n    private byte[] buildPayloadWithLongInteger(int numDigits) {\n        StringBuilder sb = new StringBuilder(numDigits + 10);\n        sb.append(\"{\\\"v\\\":\");\n        for (int i = 0; i \u003c numDigits; i++) {\n            sb.append((char) (\u00271\u0027 + (i % 9)));\n        }\n        sb.append(\u0027}\u0027);\n        return sb.toString().getBytes(StandardCharsets.UTF_8);\n    }\n}\n\n```\n\n\n### Impact\nA malicious actor can send a JSON document with an arbitrarily long number to an application using the async parser (e.g., in a Spring WebFlux or other reactive application). This can cause:\n1.  **Memory Exhaustion:** Unbounded allocation of memory in the `TextBuffer` to store the number\u0027s digits, leading to an `OutOfMemoryError`.\n2.  **CPU Exhaustion:** If the application subsequently calls `getBigIntegerValue()` or `getDecimalValue()`, the JVM can be tied up in O(n^2) `BigInteger` parsing operations, leading to a CPU-based DoS.\n\n### Suggested Remediation\n\nThe async parsing path should be updated to respect the `maxNumberLength` constraint. The simplest fix appears to ensure that `_valueComplete()` or a similar method in the async path calls the appropriate validation methods (`resetInt()` or `resetFloat()`) already present in `ParserBase`, mirroring the behavior of the synchronous parsers.\n\n**NOTE:** This research was performed in collaboration with [rohan-repos](https://github.com/rohan-repos)",
  "id": "GHSA-72hv-8253-57qq",
  "modified": "2026-08-03T20:32:01Z",
  "published": "2026-02-28T02:01:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-core/pull/1555"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-core/commit/b0c428e6f993e1b5ece5c1c3cb2523e887cd52cf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/FasterXML/jackson-core"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "jackson-core: Number Length Constraint Bypass in Async Parser Leads to Potential DoS Condition"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-18401 (GCVE-0-2026-18401)

GHSA-6QM2-MCQ7-53QP

GHSA-72HV-8253-57QQ

Summary

Details

PoC

Impact

Suggested Remediation

Tags

Sightings

Nomenclature