CVE-2026-65625

Full vulnerability record from the local CVENow database.

Description

The pure-Erlang AES-GCM fallback in jose_jwa_aes derives the number of verified authentication tag bits from the attacker-supplied tag itself. In the {aes_gcm, Bits} clause of block_decrypt/4, the incoming tag is guarded only by is_binary/1, with no check on its length. Verification in gcm_block_decrypt/6 then computes TBits = bit_size(T) and compares only those bits of the real 128-bit tag. An attacker who controls a JWE token can truncate the authentication tag to as little as 8 bits, so only 8 bits are ever checked. This reduces forgery resistance from 2^-128 to 2^-8, and a forged ciphertext is reliably accepted as authentic within 256 attempts without knowledge of the key (an authentication tag forgery and integrity bypass). Supplying a tag longer than 128 bits instead causes a badmatch that crashes the decrypting process. The fallback is reached through the public JWE decryption path whenever AES-GCM is not provided by a native crypto NIF, for example on FIPS or stripped or older OTP builds. This issue affects jose: from 1.2.0 before 1.11.13.

Severity

MEDIUM

CVSS score

5.9 (v4.0)

Vulnerability status

Received

Source identifier

6b3ad84c-e1a6-4bf7-a703-f496b71e49db

Published

2026-10-26 20:17:57.910000

Last modified

2026-10-26 20:17:57.910000

View original CVE JSON

{
  "id": "CVE-2026-65625",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "published": "2026-10-26T20:17:57.910",
  "lastModified": "2026-10-26T20:17:57.910",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The pure-Erlang AES-GCM fallback in jose_jwa_aes derives the number of verified authentication tag bits from the attacker-supplied tag itself. In the {aes_gcm, Bits} clause of block_decrypt/4, the incoming tag is guarded only by is_binary/1, with no check on its length. Verification in gcm_block_decrypt/6 then computes TBits = bit_size(T) and compares only those bits of the real 128-bit tag. An attacker who controls a JWE token can truncate the authentication tag to as little as 8 bits, so only 8 bits are ever checked. This reduces forgery resistance from 2^-128 to 2^-8, and a forged ciphertext is reliably accepted as authentic within 256 attempts without knowledge of the key (an authentication tag forgery and integrity bypass). Supplying a tag longer than 128 bits instead causes a badmatch that crashes the decrypting process. The fallback is reached through the public JWE decryption path whenever AES-GCM is not provided by a native crypto NIF, for example on FIPS or stripped or older OTP builds.\n\nThis issue affects jose: from 1.2.0 before 1.11.13."
    }
  ],
  "affected": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "affectedData": [
        {
          "vendor": "potatosalad",
          "product": "jose",
          "defaultStatus": "unaffected",
          "collectionURL": "https://repo.hex.pm",
          "packageName": "jose",
          "cpes": [
            "cpe:2.3:a:potatosalad:jose:*:*:*:*:*:*:*:*"
          ],
          "modules": [
            "jose_jwa_aes"
          ],
          "programFiles": [
            "src/jwa/jose_jwa_aes.erl"
          ],
          "programRoutines": [
            {
              "name": "jose_jwa_aes:block_decrypt/4"
            },
            {
              "name": "jose_jwa_aes:gcm_block_decrypt/6"
            }
          ],
          "repo": "https://github.com/potatosalad/erlang-jose",
          "packageURL": "pkg:hex/jose",
          "versions": [
            {
              "version": "1.2.0",
              "lessThan": "1.11.13",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "potatosalad",
          "product": "jose",
          "defaultStatus": "unaffected",
          "collectionURL": "https://github.com",
          "packageName": "potatosalad/erlang-jose",
          "cpes": [
            "cpe:2.3:a:potatosalad:jose:*:*:*:*:*:*:*:*"
          ],
          "modules": [
            "jose_jwa_aes"
          ],
          "programFiles": [
            "src/jwa/jose_jwa_aes.erl"
          ],
          "programRoutines": [
            {
              "name": "jose_jwa_aes:block_decrypt/4"
            },
            {
              "name": "jose_jwa_aes:gcm_block_decrypt/6"
            }
          ],
          "repo": "https://github.com/potatosalad/erlang-jose",
          "packageURL": "pkg:github/potatosalad/erlang-jose",
          "versions": [
            {
              "version": "8848b172575fb7d7e1e2977e8ae0a21678d2157a",
              "lessThan": "3fa1f8e3efda0da5ce6f4c9984789f979dc02740",
              "versionType": "git",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV40": [
      {
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary",
        "cvssData": {
          "version": "4.0",
          "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/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",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "vulnAvailabilityImpact": "LOW",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "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"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-354"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-65625.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/potatosalad/erlang-jose/commit/3fa1f8e3efda0da5ce6f4c9984789f979dc02740",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/potatosalad/erlang-jose/commit/8848b172575fb7d7e1e2977e8ae0a21678d2157a",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-6gxw-6f7r-cjr6",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-65625",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ]
}