# CVE-2026-2903: skvadrik re2c ast.cc check_and_merge_special_rules null pointer dereference

> A local attacker can cause a denial of service in re2c via a null pointer dereference in the AST parser.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Feb 2026
- **Updated:** 23 Jun 2026
- **Also known as:** AZL-78270, AZL-78273, BELL-CVE-2026-2903, DEBIAN-CVE-2026-2903, ECHO-3d92-841b-34e6, GHSA-7948-p5vf-r2m4, UBUNTU-CVE-2026-2903

## What is CVE-2026-2903?

CVE-2026-2903 is a medium-severity vulnerability in skvadrik re2c, published on 22 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw has been found in skvadrik re2c up to 4.4. Impacted is the function check_and_merge_special_rules of the file src/parse/ast.cc. This manipulation causes null pointer dereference. The attack can only be executed locally. The exploit has been published and may be used. Patch name: febeb977936f9519a25d9fbd10ff8256358cdb97. It is suggested to install a patch to address this issue.

Weakness: CWE-476 (NULL Pointer Dereference), CWE-404 (Improper Resource Shutdown or Release)

## Which versions are affected by CVE-2026-2903?


## How do I fix CVE-2026-2903?

Apply the vendor's patch.

## Is CVE-2026-2903 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2903 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2903 and fix it if it is affected.

What it is: CVE-2026-2903 is a medium-severity vulnerability in skvadrik re2c, published on 22 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2903 exists.

Affected product: skvadrik re2c. 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-2026-2903/ (Markdown: https://insights.sbomify.com/CVE-2026-2903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2903
- OSV: https://osv.dev/vulnerability/CVE-2026-2903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2903/
Summaries are generated and may contain mistakes; the official description above is the record.