Vulnerability-Lookup

CVE-2026-16317 (GCVE-0-2026-16317)

Vulnerability from cvelistv5 – Published: 2026-07-21 20:12 – Updated: 2026-07-21 20:16

Title

Silent Drop of TLS 1.3 Encrypted Records in s2n-tls

Summary

Missing validation of the outer content_type byte on TLS 1.3 encrypted records in s2n-tls allows an active man-in-the-middle to silently discard individual application data records without either endpoint detecting the modification. RFC 8446 Section 5.2 requires that the outer content_type of all encrypted TLS 1.3 records must be application_data (0x17). The s2n-tls AEAD implementation hardcodes this value in the additional authenticated data rather than using the actual wire byte, so the outer content_type is not covered by the authentication tag. This enables selective suppression of application data. In HTTP pipelining scenarios, dropping a TLS record containing an HTTP request can cause request/response desynchronization, where subsequent responses are delivered to the wrong requests. In write-heavy workloads, a dropped record containing a write request can result in undetectable data loss when the client interprets a subsequent success response as confirmation of the dropped write. All TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected. We recommend you upgrade s2n-tls to version v1.7.6

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L

8.3 (High)


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

CWE

CWE-354 - Improper validation of integrity check value

Assigner

AMZN

References

3 references

URL	Tags
https://github.com/aws/s2n-tls/releases/tag/v1.7.6	release-notespatch
https://aws.amazon.com/security/security-bulletin…	vendor-advisory
https://github.com/aws/s2n-tls/security/advisorie…	release-notes

Impacted products

1 product

Vendor	Product	Version
AWS	s2n-tls	Affected: 0 , ≤ 1.7.5 (custom)

Show details on NVD website

JSON

To clipboard

{
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        {
          "defaultStatus": "unaffected",
          "product": "s2n-tls",
          "vendor": "AWS",
          "versions": [
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              "status": "affected",
              "version": "0",
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      "cpeApplicability": [
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              "cpeMatch": [
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              "value": "\u003cp\u003eMissing validation of the outer content_type byte on TLS 1.3 encrypted records in s2n-tls allows an active man-in-the-middle to silently discard individual application data records without either endpoint detecting the modification. RFC 8446 Section 5.2 requires that the outer content_type of all encrypted TLS 1.3 records must be application_data (0x17). The s2n-tls AEAD implementation hardcodes this value in the additional authenticated data rather than using the actual wire byte, so the outer content_type is not covered by the authentication tag. \u003c/p\u003e\u003cp\u003eThis enables selective suppression of application data. In HTTP pipelining scenarios, dropping a TLS record containing an HTTP request can cause request/response desynchronization, where subsequent responses are delivered to the wrong requests. In write-heavy workloads, a dropped record containing a write request can result in undetectable data loss when the client interprets a subsequent success response as confirmation of the dropped write.\u003c/p\u003e\u003cp\u003eAll TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected.\u003c/p\u003e\u003cp\u003eWe recommend you upgrade s2n-tls to version v1.7.6\u003c/p\u003e"
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            "confidentialityImpact": "NONE",
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      "providerMetadata": {
        "dateUpdated": "2026-07-21T20:16:25.683Z",
        "orgId": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
        "shortName": "AMZN"
      },
      "references": [
        {
          "tags": [
            "release-notes",
            "patch"
          ],
          "url": "https://github.com/aws/s2n-tls/releases/tag/v1.7.6"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://aws.amazon.com/security/security-bulletins/2026-062-aws/"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://github.com/aws/s2n-tls/security/advisories/GHSA-684c-v35q-fvx7"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Silent Drop of TLS 1.3 Encrypted Records in s2n-tls",
      "x_generator": {
        "engine": "Vulnogram 1.0.4"
      }
    }
  },
  "cveMetadata": {
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    "assignerShortName": "AMZN",
    "cveId": "CVE-2026-16317",
    "datePublished": "2026-07-21T20:12:48.047Z",
    "dateReserved": "2026-07-20T16:40:27.027Z",
    "dateUpdated": "2026-07-21T20:16:25.683Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "cve": "CVE-2026-16317",
      "date": "2026-07-22",
      "epss": "0.00186",
      "percentile": "0.08447"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-16317\",\"sourceIdentifier\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\",\"published\":\"2026-07-21T21:16:49.060\",\"lastModified\":\"2026-07-21T21:16:49.060\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Missing validation of the outer content_type byte on TLS 1.3 encrypted records in s2n-tls allows an active man-in-the-middle to silently discard individual application data records without either endpoint detecting the modification. RFC 8446 Section 5.2 requires that the outer content_type of all encrypted TLS 1.3 records must be application_data (0x17). The s2n-tls AEAD implementation hardcodes this value in the additional authenticated data rather than using the actual wire byte, so the outer content_type is not covered by the authentication tag. \\n\\n\\n\\nThis enables selective suppression of application data. In HTTP pipelining scenarios, dropping a TLS record containing an HTTP request can cause request/response desynchronization, where subsequent responses are delivered to the wrong requests. In write-heavy workloads, a dropped record containing a write request can result in undetectable data loss when the client interprets a subsequent success response as confirmation of the dropped write.\\n\\n\\n\\nAll TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected.\\n\\n\\n\\nWe recommend you upgrade s2n-tls to version v1.7.6\"}],\"affected\":[{\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\",\"affectedData\":[{\"vendor\":\"AWS\",\"product\":\"s2n-tls\",\"defaultStatus\":\"unaffected\",\"versions\":[{\"version\":\"0\",\"lessThanOrEqual\":\"1.7.5\",\"versionType\":\"custom\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/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\",\"baseScore\":8.3,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"HIGH\",\"vulnAvailabilityImpact\":\"LOW\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"LOW\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"cvssMetricV31\":[{\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L\",\"baseScore\":6.5,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":2.2,\"impactScore\":4.2}]},\"weaknesses\":[{\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-354\"}]}],\"references\":[{\"url\":\"https://aws.amazon.com/security/security-bulletins/2026-062-aws/\",\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\"},{\"url\":\"https://github.com/aws/s2n-tls/releases/tag/v1.7.6\",\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\"},{\"url\":\"https://github.com/aws/s2n-tls/security/advisories/GHSA-684c-v35q-fvx7\",\"source\":\"ff89ba41-3aa1-4d27-914a-91399e9639e5\"}]}}",
    "redhat_vex": {
      "current_release_date": "2026-07-22T12:06:42+00:00",
      "cve": "CVE-2026-16317",
      "id": "CVE-2026-16317",
      "initial_release_date": "2026-07-21T20:12:48.047000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "s2n-tls: s2n-tls: Undetectable data loss via man-in-the-middle attack on TLS 1.3 records",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-16317.json",
      "version": "3"
    }
  }
}

FKIE_CVE-2026-16317

Vulnerability from fkie_nvd - Published: 2026-07-21 21:16 - Updated: 2026-07-21 21:16

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L

Summary

References

	URL	Tags
	ff89ba41-3aa1-4d27-914a-91399e9639e5	https://aws.amazon.com/security/security-bulletins/2026-062-aws/
	ff89ba41-3aa1-4d27-914a-91399e9639e5	https://github.com/aws/s2n-tls/releases/tag/v1.7.6
	ff89ba41-3aa1-4d27-914a-91399e9639e5	https://github.com/aws/s2n-tls/security/advisories/GHSA-684c-v35q-fvx7

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "s2n-tls",
          "vendor": "AWS",
          "versions": [
            {
              "lessThanOrEqual": "1.7.5",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Missing validation of the outer content_type byte on TLS 1.3 encrypted records in s2n-tls allows an active man-in-the-middle to silently discard individual application data records without either endpoint detecting the modification. RFC 8446 Section 5.2 requires that the outer content_type of all encrypted TLS 1.3 records must be application_data (0x17). The s2n-tls AEAD implementation hardcodes this value in the additional authenticated data rather than using the actual wire byte, so the outer content_type is not covered by the authentication tag. \n\n\n\nThis enables selective suppression of application data. In HTTP pipelining scenarios, dropping a TLS record containing an HTTP request can cause request/response desynchronization, where subsequent responses are delivered to the wrong requests. In write-heavy workloads, a dropped record containing a write request can result in undetectable data loss when the client interprets a subsequent success response as confirmation of the dropped write.\n\n\n\nAll TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected.\n\n\n\nWe recommend you upgrade s2n-tls to version v1.7.6"
    }
  ],
  "id": "CVE-2026-16317",
  "lastModified": "2026-07-21T21:16:49.060",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L",
          "version": "3.1"
        },
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        "impactScore": 4.2,
        "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
        "type": "Secondary"
      }
    ],
    "cvssMetricV40": [
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        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.3,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "LOW",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/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",
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        },
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        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-21T21:16:49.060",
  "references": [
    {
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
      "url": "https://aws.amazon.com/security/security-bulletins/2026-062-aws/"
    },
    {
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
      "url": "https://github.com/aws/s2n-tls/releases/tag/v1.7.6"
    },
    {
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
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  "sourceIdentifier": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
  "vulnStatus": "Received",
  "weaknesses": [
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      "type": "Secondary"
    }
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}

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-2026-16317 (GCVE-0-2026-16317)

FKIE_CVE-2026-16317

Tags

Sightings

Nomenclature