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Medium, CVSS 6.3

PHP JWT Library: RSA1_5 (RSAES-PKCS1-v1_5) decryption lacks implicit rejection, exposing a Bleichenbacher/Marvin padding oracle

GHSA-5739-39v2-5754

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (web-token/jwt-library 4.1.7, 4.0.7, 3.4.10), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Packagist web-token/jwt-library

    Affected
    < 3.4.10>= 4.0.0, < 4.0.7>= 4.1.0, < 4.1.7
    Fixed in
    4.0.7, 3.4.10, 4.1.7

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
6.3 · 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 · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Impact RSACrypt::decryptWithRSA15() (used by the RSA15 key-encryption algorithm) implements RSAES-PKCS1-v15 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 encryptedkey 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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-5739-39v2-5754

Agent brief

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# Patch Next advisory brief: GHSA-5739-39v2-5754

Advisory: PHP JWT Library: RSA1_5 (RSAES-PKCS1-v1_5) decryption lacks implicit rejection, exposing a Bleichenbacher/Marvin padding oracle
IDs: GHSA-5739-39v2-5754
Record: https://patchnext.com/advisories/ghsa-5739-39v2-5754 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: web-token/jwt-library 4.1.7, 4.0.7, 3.4.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist web-token/jwt-library: affected < 3.4.10; >= 4.0.0, < 4.0.7; >= 4.1.0, < 4.1.7; fixed in 4.0.7, 3.4.10, 4.1.7

## Suggested inspection (read-only)
- Packagist web-token/jwt-library: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on web-token/jwt-library.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5739-39v2-5754 (GitHub-reviewed advisory GHSA-5739-39v2-5754 lists affected ranges: Packagist web-token/jwt-library >=0 =4.0.0 =4.1.0 <4.1.7)

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