Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose

{
  "id": "7124b027cfce6e1b5a18b638ff155a3ab7b88b54d2634ef050dc3de5f912cc70",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-65626",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose",
    "summary": "The pure-Erlang RSAES-PKCS1-v1_5 decryption in the jose_jwa_pkcs1 module is a Bleichenbacher padding oracle. eme_pkcs1_decode/2 returns the recovered message when a decrypted block has valid PKCS#1 v1.5 padding (a leading 0x00 0x02, a padding string of at least eight non-zero bytes, and a 0x00 separator) and returns a distinct error result otherwise, and rsaes_pkcs1_decrypt/2 additionally returns {error, {badsize, _}} when the length check fails. The implementation applies no implicit-rejection countermeasure (RFC 8017 §7.2.2): it does not substitute a deterministic pseudo-random plaintext on a padding failure, so a one-bit padding-conformance signal leaks to the caller. Because the underlying modular exponentiation in dp/2 is a raw, non-blinded crypto:mod_pow/3, the padding check also stays distinguishable by timing even when an application normalizes every failure to a single error value. An unauthenticated attacker who knows only the public RSA key and can submit ciphertexts to a decryption endpoint that unwraps RSA1_5 JWE keys (or otherwise calls decrypt_private/3 with rsa_pkcs1_padding) can use this oracle to recover the plaintext of intercepted ciphertexts, such as content-encryption keys and thus the protected message, or to forge signatures, through roughly 10^4 to 10^6 adaptive chosen-ciphertext queries. This issue affects jose: from 1.3.0 before 1.11.13.",
    "evidence": "cve:CVE-2026-65626",
    "products": [
      {
        "name": {
          "value": "jose",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      },
      {
        "name": {
          "value": "jose",
          "evidence": "/containers/cna/affected/1/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-65626",
      "aliases": [
        "CVE-2026-65626"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV4_0": {
            "Safety": "NOT_DEFINED",
            "version": "4.0",
            "Recovery": "NOT_DEFINED",
            "baseScore": 5.9,
            "Automatable": "NOT_DEFINED",
            "attackVector": "LOCAL",
            "baseSeverity": "MEDIUM",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
            "providerUrgency": "NOT_DEFINED",
            "userInteraction": "NONE",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "privilegesRequired": "NONE",
            "subIntegrityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "subAvailabilityImpact": "NONE",
            "vulnAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "affected": [
        {
          "cpes": [
            "cpe:2.3:a:potatosalad:jose:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/potatosalad/erlang-jose",
          "vendor": "potatosalad",
          "modules": [
            "jose_jwa_pkcs1"
          ],
          "product": "jose",
          "versions": [
            {
              "status": "affected",
              "version": "1.3.0",
              "lessThan": "1.11.13",
              "versionType": "semver"
            }
          ],
          "packageURL": "pkg:hex/jose",
          "packageName": "jose",
          "programFiles": [
            "src/jwa/jose_jwa_pkcs1.erl"
          ],
          "collectionURL": "https://repo.hex.pm",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "jose_jwa_pkcs1:decrypt_private/3"
            },
            {
              "name": "jose_jwa_pkcs1:rsaes_pkcs1_decrypt/2"
            },
            {
              "name": "jose_jwa_pkcs1:eme_pkcs1_decode/2"
            },
            {
              "name": "jose_jwa_pkcs1:dp/2"
            }
          ]
        },
        {
          "cpes": [
            "cpe:2.3:a:potatosalad:jose:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/potatosalad/erlang-jose",
          "vendor": "potatosalad",
          "modules": [
            "jose_jwa_pkcs1"
          ],
          "product": "jose",
          "versions": [
            {
              "status": "affected",
              "version": "853c5d4c4c0bd2a7ecb055b237f4284184e176c8",
              "lessThan": "0eac8cef9aaa48fb6846f4e47a0002dc4a73966d",
              "versionType": "git"
            }
          ],
          "packageURL": "pkg:github/potatosalad/erlang-jose",
          "packageName": "potatosalad/erlang-jose",
          "programFiles": [
            "src/jwa/jose_jwa_pkcs1.erl"
          ],
          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "jose_jwa_pkcs1:decrypt_private/3"
            },
            {
              "name": "jose_jwa_pkcs1:rsaes_pkcs1_decrypt/2"
            },
            {
              "name": "jose_jwa_pkcs1:eme_pkcs1_decode/2"
            },
            {
              "name": "jose_jwa_pkcs1:dp/2"
            }
          ]
        }
      ],
      "modified": "2026-10-26T19:53:05.620Z",
      "provider": "cve",
      "references": [
        "https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-vwvr-f994-6j9j",
        "https://cna.erlef.org/cves/CVE-2026-65626.html",
        "https://osv.dev/vulnerability/EEF-CVE-2026-65626",
        "https://github.com/potatosalad/erlang-jose/commit/853c5d4c4c0bd2a7ecb055b237f4284184e176c8",
        "https://github.com/potatosalad/erlang-jose/commit/0eac8cef9aaa48fb6846f4e47a0002dc4a73966d"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
          "shortName": "EEF",
          "dateUpdated": "2026-10-26T19:53:05.620Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-65626",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 338318,
  "published_at": "2026-10-26T19:53:05.62+00:00"
}