# CVE-2026-126049: Gwenhywfar 5.14.2 Use-After-Free via GWEN_TLV_Buffer_To_DB() Nested BER-TLV Parsing


- **Severity:** Medium 5.1 (`CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 10 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** GHSA-q838-74px-f7cc

## What is CVE-2026-126049?

CVE-2026-126049 is a medium-severity vulnerability in Martin Preuss Gwenhywfar, published on 10 Nov 2026. 

### Official description

Gwenhywfar 5.14.2 contains a heap use-after-free vulnerability in GWEN_TLV_Buffer_To_DB() in src/parser/tlv.c, which frees a nested record's GWEN_DB node when parsing of its contents fails but continues processing and adds the freed node to the parent instead of returning. Attackers can supply a constructed BER-TLV record with unparseable contents, such as via a malicious chip card read by libchipcard, to corrupt heap memory.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-126049?


## How do I fix CVE-2026-126049?

No fix has been published for CVE-2026-126049 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-126049 being exploited?

There is no known exploitation of CVE-2026-126049 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126049 and fix it if it is affected.

What it is: CVE-2026-126049 is a medium-severity vulnerability in Martin Preuss Gwenhywfar, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126049 in the wild and no public exploit code.

Affected product: Martin Preuss Gwenhywfar. 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-2026-126049/ (Markdown: https://insights.sbomify.com/CVE-2026-126049/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126049
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126049
- OSV: https://osv.dev/vulnerability/CVE-2026-126049

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126049/
Summaries are generated and may contain mistakes; the official description above is the record.