PyJWT accepts public JWK containers as HMAC secrets

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-102273: 0.18% estimated exploitation activity in the next 30 days; percentile 6.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary PyJWT 2.13.0 contains an incomplete defense against algorithm confusion when an application mixes symmetric and asymmetric algorithms in one verification path. A public RSA, EC, or OKP JWK can be accepted as an HMAC secret when it is wrapped in a JWKS object, nested in an array, or represented in another container form that does not expose a top-level kty member. Impact An attacker who knows the public key material can forge HS256/HS384/HS512 tokens if the application simultaneously: allows both HS and asymmetric algorithms; passes raw public JWK/JWKS JSON as key=; and uses that same value as the HMAC secret. This can allow forged JWT claims in affected application configurations. The issue does not affect applications that keep symmetric and asymmetric verification paths separate and follow PyJWT's algorithm-selection guidance. Fix status The fix is on master in commit 801cd12 (fix: reject public JWK container HMAC keys). HMACAlgorithm.preparekey now rejects public JWK…

Published by the source

29 Sep 2026, 23:16 UTC

Last modified by the source

1 Oct 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:54 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w2cx-738m-mc7w

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-w2cx-738m-mc7w

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-w2cx-738m-mc7w

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# Patch Next advisory brief: CVE-2026-102273

Advisory: PyJWT accepts public JWK containers as HMAC secrets
IDs: CVE-2026-102273, GHSA-w2cx-738m-mc7w
Record: https://patchnext.com/advisories/cve-2026-102273 (revision 3, source checked 26 Oct 2026, 13:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pyjwt 2.14.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pyjwt: affected >= 2.13.0, <= 2.13.0; fixed in 2.14.0

## Suggested inspection (read-only)
- `python -m pip show pyjwt`: prints the installed version. Run with the environment that serves production active.

## 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 pyjwt.
- 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-w2cx-738m-mc7w (GitHub-reviewed advisory GHSA-w2cx-738m-mc7w lists affected ranges: PyPI pyjwt >=2.13.0 <=2.13.0)
- Verified: https://osv.dev/vulnerability/GHSA-w2cx-738m-mc7w (OSV record GHSA-w2cx-738m-mc7w lists affected ranges: PyPI pyjwt >=2.13.0 <2.14.0 (fixed))

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