CVE-2026-102273.

Disclosure summary

### 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.prepare_key` now rejects public JWK members found in objects, arrays, nested containers, BOM/UTF variants, and recursion-limit inputs. It also recognizes escaped JSON member names without treating ordinary strin

Source-specific records & product guidance

Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.

Original records & references

• NIST NVD record
• CVE Program record
• github.com — Reviewed advisory

PUBLISHED 2026-09-29T19:16:55-04:00
MODIFIED 2026-09-29T19:16:55-04:00
INGESTED 2026-10-06T11:43:08-04:00