CVE-2026-102272 PyJWT BOM Bypass
Attackers can forge authenticated tokens by exploiting a BOM parsing flaw in PyJWT's key detection, bypassing signature verification.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-102272?
CVE-2026-102272 is a high-severity 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, HMACAlgorithm.prepare_key in jwt/algorithms.py is affected because raw-JWK detector does not normalize accepted Unicode byte-order marks before checking for JSON. This occurs when a public JWK is prefixed with a UTF-8 BOM and used in a mixed-algorithm verification path. As a result, public JWK bypasses asymmetric-key detection and becomes the HMAC secret. Consequently, an attacker who knows the public key can forge authenticated tokens. This issue is fixed in version 2.14.0.
Weakness: CWE-347
Which versions are affected by CVE-2026-102272?
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-2026-102272?
Upgrade pyjwt to 2.14.0 or later.
Is CVE-2026-102272 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102272 exists.
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-105224, CLEANSTART-2026-GJ26931, CLEANSTART-2026-YQ31003, DEBIAN-CVE-2026-102272, ECHO-20d5-2851-e01f, GHSA-r6x4-923q-g947 and 17 more.