Authentication policy bypass via ignored critical headers
Published Mar 12, 2026 · Updated Mar 12, 2026
Improper JWS validation in PyJWT before 2.12.0 allows remote attackers to bypass token security policies via unsupported critical headers. The decode path returns a verified payload without rejecting a crit array that names header extensions it does not understand or process. Impact requires an application to assign enforcement semantics to such an extension, allowing validly signed tokens to evade MFA, token-binding, or scope controls.
Summary
What happened
Improper JWS validation in PyJWT before 2.12.0 allows remote attackers to bypass token security policies via unsupported critical headers. The decode path returns a verified payload without rejecting a crit array that names header extensions it does not understand or process. Impact requires an application to assign enforcement semantics to such an extension, allowing validly signed tokens to evade MFA, token-binding, or scope controls.
The record
- CVE
- CVE-2026-32597
- Published
- Mar 12, 2026
- Updated
- Mar 12, 2026
- Vendor
- Jose Padilla
- Product
- PyJWT
- Classifications
- CWE-345, CWE-863
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 12, 2026CVE publishedPublication date reported by the CVE source.
- Mar 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.12.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-752w-5fwx-jx9f proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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