CVE-2026-103001 PyJWT.decode() reintroduces options-dict mutation, enabling silent claim-verification bypass on dict reuse
Attackers can bypass JWT claim verification by exploiting mutable options dictionary reuse in PyJWT, allowing acceptance of invalid tokens.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-103001?
CVE-2026-103001 is a medium-severity vulnerability in jpadilla pyjwt, published on 30 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 2.11.0 through 2.13.0, PyJWT's PyJWT._merge_options() method can modify a caller-supplied mutable options mapping when verify_signature is false. If an application reuses that same mapping for a later decode() or decode_complete() call and changes verify_signature to true, the mapping can retain false values for expiration, not-before, issued-at, audience, issuer, subject, and JWT ID checks. A signed token with invalid registered claims can then be accepted without disabling signature verification, but applications that create a fresh options mapping for each call are not affected.
Weakness: CWE-471
Which versions are affected by CVE-2026-103001?
3 open source packages ship an affected version, including pyjwt and PyJWT. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pyjwt PyPI | From 2.11.0 to 2.13.0 | None |
pyjwt PyPI | From 2.11.0 to 2.13.0 | None |
PyJWT PyPI | From 2.11.0 to 2.13.0 | None |
Products include Pyjwt Project Pyjwt.
How do I fix CVE-2026-103001?
Upgrade to a fixed version.
Is CVE-2026-103001 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-103001 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-105642, BELL-CVE-2026-103001, CLEANSTART-2026-AF59744, CLEANSTART-2026-CW76652, DEBIAN-CVE-2026-103001, ECHO-8665-d21f-1204 and 25 more.