# CVE-2026-109831: UnRTF out-of-bounds write

Source: https://junglewise.ai/threats/cve-2026-109831-unrtf-by-gnu-project-is-vulnerable-to-out-of-bounds-write-if-a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-109831 · Severity: medium · CVSS 5.4 · Published 2026-10-20

UnRTF is a document converter that transforms Rich Text Format (RTF) files into other formats. A crafted RTF file can trigger an out-of-bounds write vulnerability, causing the application to crash and denying users access to the conversion service or potentially corrupting data.

Vendors: [GNU Project](https://junglewise.ai/threats/vendors/gnu-project).

## Quick answers

**Is CVE-2026-109831 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109831 being exploited in the wild.

**How severe is CVE-2026-109831?** Medium severity, with a CVSS score of 5.4, published 20 October 2026.

**Which products and versions are affected?** GNU Project UnRTF prior to 0.21.12.

**Is there a fix for CVE-2026-109831?** Yes: fixed in 0.21.12. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-109831 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-109831?** Check whether you run GNU Project UnRTF at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 0.21.12

## Technical details

UnRTF contains an out-of-bounds write vulnerability (CWE-787) triggered by parsing maliciously crafted RTF files. The attack requires user interaction (opening a malicious RTF file) over the network. Successful exploitation results in denial-of-service through application crash and potential data integrity issues.

## Affected products

- GNU Project UnRTF prior to 0.21.12

## Timeline

- 2026-10-20: disclosed
- 2026-08-24: patched: UnRTF 0.21.12 released

## References

- [https://jvn.jp/en/jp/JVN29783594/](https://jvn.jp/en/jp/JVN29783594/)
- [https://savannah.gnu.org/news/?id=10925](https://savannah.gnu.org/news/?id=10925)