Executive brief
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.
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