Vulnerability · Published Aug 10, 2026 · Assigned by CERT-PL
CVE-2026-71391Off-by-One Error in GNU Emacs for Android
Medium 5.3
In plain English
A medium-severity security flaw in Emacs from GNU. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 46% of all known vulnerabilities).
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
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | emacs | no fix listed | DEBIAN-CVE-2026-71391 |
| Debian:13 | emacs | no fix listed | DEBIAN-CVE-2026-71391 |
| Debian:14 | emacs | no fix listed | DEBIAN-CVE-2026-71391 |
| Ubuntu:26.10 | emacs | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:22.04:LTS | xemacs21 | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:24.04:LTS | xemacs21 | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:26.04:LTS | xemacs21 | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:26.10 | xemacs21 | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:22.04:LTS | xemacs21-packages | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:24.04:LTS | xemacs21-packages | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:26.04:LTS | xemacs21-packages | no fix listed | UBUNTU-CVE-2026-71391 |
| Ubuntu:26.10 | xemacs21-packages | no fix listed | UBUNTU-CVE-2026-71391 |
Affected products (as reported)
Weakness: CWE-193 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N