CVE-2026-58226 (GCVE-0-2026-58226)

Vulnerability from cvelistv5 – Published: 2026-07-06 09:03 – Updated: 2026-07-06 14:04
VLAI
Title
Unauthenticated denial-of-service via unbounded HPACK integer decoding in hpax
Summary
Inefficient Algorithmic Complexity vulnerability in elixir-mint hpax allows unauthenticated denial-of-service via unbounded HPACK integer decoding. hpax decodes HPACK variable-length integers with no upper bound on the decoded value or the number of continuation octets. 'Elixir.HPAX.Types':decode_remaining_integer/3 accumulates the integer as int + (value <<< m), shifting by 7 more bits for each continuation octet and stopping only on a terminating octet or truncated input, never because the integer grew too large. Because BEAM integers are arbitrary precision, a run of N continuation octets builds an O(N)-bit bignum and re-adds into an ever-larger bignum on each step, so the total decoding cost is superlinear (about O(N^2)). An unauthenticated attacker who can send an HTTP/2 header block to a server using this decoder (reached through the 'Elixir.HPAX':decode/2 entry point) can supply a small header block that forces a large, attacker-controlled amount of CPU (and transient memory), a denial-of-service amplification. This issue affects hpax from 0.1.1 before 1.0.4.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SSVC
Exploitation: poc Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-06 12:49 UTC
CWE
  • CWE-407 - Inefficient Algorithmic Complexity
Assigner
References
Impacted products
Vendor Product Version CPE status
elixir-mint hpax Affected: 0.1.1 , < 1.0.4 (semver)
    cpe:2.3:a:elixir-mint:hpax:*:*:*:*:*:*:*:*
Create a notification for this product.
elixir-mint hpax Affected: 56db437a7e2c515e3bdd770ac7947b02cd2390d0 , < 1ba4bb2dc91e80089cf89c73970ac3ded76f17eb (git)
    cpe:2.3:a:elixir-mint:hpax:*:*:*:*:*:*:*:*
Create a notification for this product.
Credits
Peter Ullrich Andrea Leopardi Jonatan Männchen / EEF Eric Meadows-Jönsson
Show details on NVD website
To clipboard 

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              "defaultStatus": "unaffected",
              "modules": [
                "Elixir.HPAX",
                "Elixir.HPAX.Types"
              ],
              "packageName": "elixir-mint/hpax",
              "packageURL": "pkg:github/elixir-mint/hpax",
              "product": "hpax",
              "programFiles": [
                "lib/hpax.ex",
                "lib/hpax/types.ex"
              ],
              "programRoutines": [
                {
                  "name": "\u0027Elixir.HPAX\u0027:decode/2"
                },
                {
                  "name": "\u0027Elixir.HPAX.Types\u0027:decode_integer/2"
                },
                {
                  "name": "\u0027Elixir.HPAX.Types\u0027:decode_remaining_integer/3"
                }
              ],
              "repo": "https://github.com/elixir-mint/hpax",
              "vendor": "elixir-mint",
              "versions": [
                {
                  "lessThan": "1ba4bb2dc91e80089cf89c73970ac3ded76f17eb",
                  "status": "affected",
                  "version": "56db437a7e2c515e3bdd770ac7947b02cd2390d0",
                  "versionType": "git"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:a:elixir-mint:hpax:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "1.0.4",
                      "versionStartIncluding": "0.1.1",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "AND"
                }
              ],
              "operator": "OR"
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "finder",
              "value": "Peter Ullrich"
            },
            {
              "lang": "en",
              "type": "remediation developer",
              "value": "Andrea Leopardi"
            },
            {
              "lang": "en",
              "type": "analyst",
              "value": "Jonatan M\u00e4nnchen / EEF"
            },
            {
              "lang": "en",
              "type": "analyst",
              "value": "Eric Meadows-J\u00f6nsson"
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cp\u003eInefficient Algorithmic Complexity vulnerability in elixir-mint hpax allows unauthenticated denial-of-service via unbounded HPACK integer decoding.\u003c/p\u003e\u003cp\u003e\u003ctt\u003ehpax\u003c/tt\u003e decodes HPACK variable-length integers with no upper bound on the decoded value or the number of continuation octets. \u003ctt\u003e\u0027Elixir.HPAX.Types\u0027:decode_remaining_integer/3\u003c/tt\u003e accumulates the integer as \u003ctt\u003eint + (value \u0026lt;\u0026lt;\u0026lt; m)\u003c/tt\u003e, shifting by 7 more bits for each continuation octet and stopping only on a terminating octet or truncated input, never because the integer grew too large. Because BEAM integers are arbitrary precision, a run of N continuation octets builds an O(N)-bit bignum and re-adds into an ever-larger bignum on each step, so the total decoding cost is superlinear (about O(N^2)). An unauthenticated attacker who can send an HTTP/2 header block to a server using this decoder (reached through the \u003ctt\u003e\u0027Elixir.HPAX\u0027:decode/2\u003c/tt\u003e entry point) can supply a small header block that forces a large, attacker-controlled amount of CPU (and transient memory), a denial-of-service amplification.\u003c/p\u003e\u003cp\u003eThis issue affects \u003ctt\u003ehpax\u003c/tt\u003e from 0.1.1 before 1.0.4.\u003c/p\u003e"
                }
              ],
              "value": "Inefficient Algorithmic Complexity vulnerability in elixir-mint hpax allows unauthenticated denial-of-service via unbounded HPACK integer decoding.\n\nhpax decodes HPACK variable-length integers with no upper bound on the decoded value or the number of continuation octets. \u0027Elixir.HPAX.Types\u0027:decode_remaining_integer/3 accumulates the integer as int + (value \u003c\u003c\u003c m), shifting by 7 more bits for each continuation octet and stopping only on a terminating octet or truncated input, never because the integer grew too large. Because BEAM integers are arbitrary precision, a run of N continuation octets builds an O(N)-bit bignum and re-adds into an ever-larger bignum on each step, so the total decoding cost is superlinear (about O(N^2)). An unauthenticated attacker who can send an HTTP/2 header block to a server using this decoder (reached through the \u0027Elixir.HPAX\u0027:decode/2 entry point) can supply a small header block that forces a large, attacker-controlled amount of CPU (and transient memory), a denial-of-service amplification.\n\nThis issue affects hpax from 0.1.1 before 1.0.4."
            }
          ],
          "impacts": [
            {
              "capecId": "CAPEC-130",
              "descriptions": [
                {
                  "lang": "en",
                  "value": "CAPEC-130 Excessive Allocation"
                }
              ]
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 8.7,
                "baseSeverity": "HIGH",
                "privilegesRequired": "NONE",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "NONE",
                "vulnIntegrityImpact": "NONE"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-407",
                  "description": "CWE-407 Inefficient Algorithmic Complexity",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-07-06T14:04:14.632Z",
            "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "shortName": "EEF"
          },
          "references": [
            {
              "tags": [
                "vendor-advisory",
                "related"
              ],
              "url": "https://github.com/elixir-mint/hpax/security/advisories/GHSA-jj2p-32j7-whj2"
            },
            {
              "tags": [
                "related"
              ],
              "url": "https://cna.erlef.org/cves/CVE-2026-58226.html"
            },
            {
              "tags": [
                "related"
              ],
              "url": "https://osv.dev/vulnerability/EEF-CVE-2026-58226"
            },
            {
              "tags": [
                "patch"
              ],
              "url": "https://github.com/elixir-mint/hpax/commit/1ba4bb2dc91e80089cf89c73970ac3ded76f17eb"
            }
          ],
          "source": {
            "discovery": "EXTERNAL"
          },
          "title": "Unauthenticated denial-of-service via unbounded HPACK integer decoding in hpax",
          "x_generator": {
            "engine": "cvelib 1.8.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "assignerShortName": "EEF",
        "cveId": "CVE-2026-58226",
        "datePublished": "2026-07-06T09:03:47.374Z",
        "dateReserved": "2026-06-29T18:54:08.633Z",
        "dateUpdated": "2026-07-06T14:04:14.632Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.