GHSA-5739-39v2-5754

Suggest an improvement
Source
https://github.com/advisories/GHSA-5739-39v2-5754
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-5739-39v2-5754
Downstream
Published
2026-06-18T21:09:56Z
Modified
2026-08-31T15:00:08Z
Severity
  • 6.3 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N CVSS Calculator
Summary
PHP JWT Library: RSA1_5 (RSAES-PKCS1-v1_5) decryption lacks implicit rejection, exposing a Bleichenbacher/Marvin padding oracle
Details

Impact

RSACrypt::decryptWithRSA15() (used by the RSA1_5 key-encryption algorithm) implements RSAES-PKCS1-v1_5 decryption by inspecting the padding after RSADP and throwing InvalidArgumentException as soon as the padding is malformed. It does not implement the implicit-rejection countermeasure required by RFC 3447 §7.2.2 / RFC 8017 §7.1.2 (return a deterministic pseudo-random value of the expected length on padding failure and let the downstream step fail uniformly).

From a JWE caller this yields a Bleichenbacher/Marvin padding oracle: an attacker submitting adaptively crafted encrypted_key values can distinguish (a) padding rejected, (b) padding valid but wrong CEK length, and (c) padding valid and full AEAD executed — even though JWEDecrypter returns the same false in all cases — because each path performs a measurably different amount of work, amplifiable by enlarging the ciphertext (CWE-208 timing side channel). Enough adaptive queries can recover the wrapped CEK.

Affected configurations

Applications that register RSA1_5 in their decryption AlgorithmManager and hold an RSA private key.

Patches

PKCS#1 v1.5 decryption now performs implicit rejection: on invalid padding (or unexpected recovered length) it returns a random CEK of the expected size selected in constant time, so the full content-decryption (AEAD) step always runs and fails uniformly, removing the observable difference between padding-valid and padding-invalid ciphertexts. Users are still strongly encouraged to migrate to RSA-OAEP.

Workarounds

Prefer RSA-OAEP/RSA-OAEP-256; do not enable RSA1_5 for untrusted tokens.

References

  • RFC 3447 §7.2.2 / RFC 8017 §7.1.2
  • Bleichenbacher (1998); Marvin attack
  • CWE-208: Observable Timing Discrepancy

Résolution

Un correctif a été préparé sur une branche dédiée basée sur 3.4.x, avec des tests anti-régression dédiés (fork privé temporaire de cette advisory, PR #1).

RSA1_5 — déchiffrement PKCS#1 v1.5 avec implicit rejection en temps constant (RFC 3447 §7.2.2) : un padding invalide n'est plus distinguable d'un padding valide, neutralisant l'oracle Bleichenbacher.

Validation : php -l OK, PHPUnit vert, aucune nouvelle erreur PHPStan introduite (différentiel nul vs 3.4.x), aucun commentaire ajouté dans le code source. Après merge, cascade prévue 3.4.x → 4.0.x → 4.1.x.

Database specific 
{
    "cwe_ids": [
        "CWE-208",
        "CWE-385"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-18T21:09:56Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
}
References

Affected packages

Packagist / web-token/jwt-library

Package

Name
web-token/jwt-library
Purl
pkg:composer/web-token/jwt-library

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
3.4.10

Affected versions

3.*
3.3.0
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.4.0
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.4.6
3.4.7
3.4.8
3.4.9

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json"

Packagist / web-token/jwt-library

Package

Name
web-token/jwt-library
Purl
pkg:composer/web-token/jwt-library

Affected ranges

Type
ECOSYSTEM
Events
Introduced
4.0.0
Fixed
4.0.7

Affected versions

4.*
4.0.0
4.0.1
4.0.2
4.0.3
4.0.4
4.0.5
4.0.6

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json"

Packagist / web-token/jwt-library

Package

Name
web-token/jwt-library
Purl
pkg:composer/web-token/jwt-library

Affected ranges

Type
ECOSYSTEM
Events
Introduced
4.1.0
Fixed
4.1.7

Affected versions

4.*
4.1.0
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-5739-39v2-5754/GHSA-5739-39v2-5754.json"