CVE-2026-102273 PyJWT accepts public JWK containers as HMAC secrets
Attackers can forge JWT tokens with arbitrary claims by exploiting HMAC key validation flaws in PyJWT when mixed algorithms are enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-102273?
CVE-2026-102273 is a high-severity authentication bypass vulnerability in jpadilla pyjwt, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because HMAC key guard only recognizes top-level public JWK forms and misses container representations. This occurs when an application allows HMAC and asymmetric algorithms and passes a public JWK container as the raw key. As a result, public asymmetric key material is accepted as the HMAC secret. Consequently, an attacker who knows the public key can forge a token with arbitrary authenticated claims. This issue is fixed in version 2.14.0.
Weakness: CWE-347
Which versions are affected by CVE-2026-102273?
3 open source packages ship an affected version, including pyjwt and PyJWT. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pyjwt PyPI | From 2.13.0 | 2.14.0 |
pyjwt PyPI | From 2.13.0 | 2.14.0 |
PyJWT PyPI | From 2.13.0 | 2.14.0 |
Products include Pyjwt Project Pyjwt.
How do I fix CVE-2026-102273?
Upgrade pyjwt to 2.14.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-102273 being exploited?
There is no known exploitation of CVE-2026-102273 in the wild and no public exploit code.
Other vulnerabilities in jpadilla pyjwt
- CVE-2026-102268 PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard
- CVE-2026-32597 PyJWT accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)
- CVE-2026-102266 PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
- CVE-2026-102267 PyJWT: PyJWKClient follows redirects when fetching JWKS
- CVE-2026-102271 PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard
Sources
Also known as AZL-105227, CLEANSTART-2026-FP98505, CLEANSTART-2026-TY25430, DEBIAN-CVE-2026-102273, ECHO-aa39-5d33-5a5c, GHSA-w2cx-738m-mc7w and 17 more.