GNU Emacs up to 30.2 Gvar Table Parser src/sfnt.c sfnt_vary_simple_glyph/sfnt_vary_compound_glyph off-by-one

Summaryinfo

A vulnerability identified as critical has been detected in GNU Emacs up to 30.2. This affects the function sfnt_vary_simple_glyph/sfnt_vary_compound_glyph of the file src/sfnt.c of the component Gvar Table Parser. The manipulation leads to off-by-one. This vulnerability is traded as CVE-2026-71391. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in GNU Emacs up to 30.2. This issue affects the function sfnt_vary_simple_glyph/sfnt_vary_compound_glyph of the file src/sfnt.c of the component Gvar Table Parser. The manipulation with an unknown input leads to a off-by-one vulnerability. Using CWE to declare the problem leads to CWE-193. A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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

The advisory is shared at cert.pl. The identification of this vulnerability is CVE-2026-71391 since 08/06/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available.

Applying the patch 95ab9ef627b212d74d321c5bbb5b56a1be7b9fbe is able to eliminate this problem.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-2721). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Open Source GNU Emacs

Productinfo

Type

• Word Processing Software

Vendor

• GNU

Name

• Emacs

Version

• 30.0
• 30.1
• 30.2

License

• open-source

Website

• Vendor: https://www.gnu.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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