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

> A crafted JWK file with integer values instead of strings causes a null pointer dereference in LibJWT, leading to denial of service.

- **Severity:** Medium 5.8 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 27 Mar 2026
- **Updated:** 31 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-33996, GHSA-ph96-hqpc-9f66, UBUNTU-CVE-2026-33996

## What is CVE-2026-33996?

CVE-2026-33996 is a medium-severity vulnerability in benmcollins libjwt, published on 27 Mar 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-33996?

It affects 1 product.


Products: Libjwt Libjwt.

## How do I fix CVE-2026-33996?

Upgrade to a fixed version.

## Is CVE-2026-33996 being exploited?

There is no known exploitation of CVE-2026-33996 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33996 and fix it if it is affected.

What it is: CVE-2026-33996 is a medium-severity vulnerability in benmcollins libjwt, published on 27 Mar 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-33996 in the wild and no public exploit code.

Affected product: benmcollins libjwt. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33996/ (Markdown: https://insights.sbomify.com/CVE-2026-33996/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33996
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33996
- OSV: https://osv.dev/vulnerability/CVE-2026-33996

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33996/
Summaries are generated and may contain mistakes; the official description above is the record.