CVE-2026-71391 Off-by-One Error in GNU Emacs for Android
A crafted TrueType font triggers an off-by-one error in GNU Emacs for Android, allowing heap memory disclosure to defeat ASLR.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-71391?
CVE-2026-71391 is a medium-severity memory corruption vulnerability in GNU Emacs, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
GNU Emacs for Android contains an off-by-one error in the gvar table parser in src/sfnt.c. The shared-coordinate index boundary check in sfnt_vary_simple_glyph() and sfnt_vary_compound_glyph() uses a strict greater-than comparison instead of greater-than-or-equal, allowing a crafted TrueType variable font to bypass the check and trigger a heap-based out-of-bounds read via memcpy. An attacker can deliver a malicious font file via email, EWW (Emacs Web Wowser), or documents with custom faces, causing Emacs to load it. This exposes heap memory contents which can be later used to defeat ASLR.
This issue was fixed in commit 95ab9ef627b212d74d321c5bbb5b56a1be7b9fbe
Weakness: CWE-193
Which versions are affected by CVE-2026-71391?
How do I fix CVE-2026-71391?
No fix has been published for CVE-2026-71391 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-71391 being exploited?
There is no known exploitation of CVE-2026-71391 in the wild and no public exploit code.
Sources
Also known as GHSA-49vj-r7f8-c3p6, UBUNTU-CVE-2026-71391.