Bug 2513076 (CVE-2026-71391)

Summary: CVE-2026-71391 emacs: off-by-one error via a malicious font file
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in GNU Emacs, specifically in GNU Emacs for Android. An off-by-one error can occur when a specially crafted font file is processed due to an improper bounds check. This can cause a heap-based buffer over-read, exposing heap memory contents.
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Description OSIDB Bzimport 2026-08-10 10:31:28 UTC 
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