# CVE-2026-71392: GNU Emacs integer overflow in sfnt_read_cmap_format_12

Source: https://junglewise.ai/threats/cve-2026-71392-gnu-emacs-integer-overflow-in-sfnt-read-cmap-format-12  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-10. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-71392 · Severity: info · CVSS 7.3 · Published 2026-08-10

GNU Emacs, a text editor commonly used by developers and system administrators, contains a vulnerability in how it processes TrueType font files. An attacker can deliver a malicious font file through email, web content, or documents, causing Emacs to crash or execute arbitrary code. This impacts any system where Emacs loads untrusted fonts.

Technologies: [Gnu Emacs](https://junglewise.ai/threats/technologies/emacs). Vendors: [Gnu](https://junglewise.ai/threats/vendors/gnu).

## Quick answers

**Is CVE-2026-71392 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-71392 being exploited in the wild.

**How severe is CVE-2026-71392?** Informational severity, with a CVSS score of 7.3, published 10 August 2026.

**Which products and versions are affected?** Gnu Emacs through 30.2.

**Is there a fix for CVE-2026-71392?** A patch was published on 2026-08-10: Fixed in commit c4e20777c26548722a37b03db93243e83a0d6188 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-71392 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-71392?** Check whether you run Gnu Emacs 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.

## Technical details

The vulnerability is an integer overflow (CWE-190) in the sfnt_read_cmap_format_12() function in src/sfnt.c. When processing a crafted TrueType font file, an unguarded addition in an xmalloc allocation call wraps around on 32-bit builds, causing a heap buffer overflow write. An attacker delivers a malicious font file via email, EWW (Emacs Web Wowser), or documents with custom faces, triggering Emacs to load it. The resulting heap memory corruption can lead to code execution. The fix is available in commit c4e20777c26548722a37b03db93243e83a0d6188.

## Affected products

- GNU Emacs through 30.2

## Timeline

- 2026-08-10: disclosed
- 2026-08-10: patched: Fixed in commit c4e20777c26548722a37b03db93243e83a0d6188

## References

- [https://cert.pl/en/posts/2026/08/CVE-2026-71391](https://cert.pl/en/posts/2026/08/CVE-2026-71391)
- [https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=c4e20777c26548722a37b03db93243e83a0d6188](https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=c4e20777c26548722a37b03db93243e83a0d6188)

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