Application crash via unchecked JWK string conversion
Published Mar 27, 2026 · Updated Mar 27, 2026
NULL pointer dereference in LibJWT allows attackers to crash JWK-processing applications by supplying a malformed RSA-PSS or octet JWK. The RSA parser converts a non-string alg member to NULL and reads its first byte, while octet parsing passes an unchecked NULL string into Base64URL decoding. Exploitation requires an application or user to import attacker-controlled JWK data, and the resulting failure interrupts that consuming process.
Summary
What happened
NULL pointer dereference in LibJWT allows attackers to crash JWK-processing applications by supplying a malformed RSA-PSS or octet JWK. The RSA parser converts a non-string alg member to NULL and reads its first byte, while octet parsing passes an unchecked NULL string into Base64URL decoding. Exploitation requires an application or user to import attacker-controlled JWK data, and the resulting failure interrupts that consuming process.
The record
- CVE
- CVE-2026-33996
- Published
- Mar 27, 2026
- Updated
- Mar 27, 2026
- Vendor
- LibJWT
- Product
- LibJWT
- Classifications
- CWE-476, T1499.004
- Attack vector
- adjacent
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 27, 2026CVE publishedPublication date reported by the CVE source.
- Mar 27, 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?
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- Affected versionversion=>= 3.0.0, < 3.3.0
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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