CVE-2026-71393
Received Received - Intake

Integer Overflow Leading to Heap Buffer Overflow in GNU Emacs for Android

Publication date: 2026-08-10

Last updated on: 2026-08-10

Assigner: CERT.PL

Description
GNU Emacs for Android is vulnerable to an integer overflow in sfnt_read_name_table() in src/sfnt.c. The function computes an allocation size using a 32-bit length value from a TrueType font file without overflow checking. On 32-bit targets, a crafted font causes the calculation to wrap, resulting in an undersized heap allocation. A subsequent read() call writes beyond the buffer, causing a heap buffer overflow. 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 can lead to heap memory corruption and potential code execution. This issue was fixed in commit d51a4722316efe0960994d371e1859099894d1ca

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Meta Information

Published
2026-08-10
Last Modified
2026-08-10
Generated
2026-08-10
AI Q&A
2026-08-10
EPSS Evaluated
N/A
NVD
CVE-2026-71393
EUVD
EUVD-2026-55258

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
gnu emacs *
gnu emacs to 2026-08-01 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-190 The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

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Executive Summary

GNU Emacs for Android has an integer overflow in the sfnt_read_name_table() function in src/sfnt.c. The function calculates memory allocation size using a 32-bit value from a TrueType font file without checking for overflow. On 32-bit systems, a crafted font can cause the calculation to wrap, leading to an undersized heap allocation. A read() call then writes beyond the buffer, causing a heap buffer overflow. Attackers can exploit this by delivering malicious font files via email, EWW, or documents with custom faces, triggering memory corruption and potential code execution.

Detection Guidance

This vulnerability involves a heap buffer overflow in GNU Emacs for Android due to an integer overflow in font processing. Detection requires checking Emacs versions and analyzing font files for malicious content. No direct network detection commands exist, but you can inspect Emacs binaries for the vulnerable function and monitor for crashes during font rendering.

Impact Analysis

This vulnerability allows attackers to execute arbitrary code on your device by tricking you into opening a malicious font file. It could lead to data theft, system compromise, or further malware installation. Users of GNU Emacs for Android on 32-bit systems are most at risk.

Compliance Impact

This vulnerability could lead to unauthorized data access or exfiltration, violating GDPR's data protection principles or HIPAA's security requirements. Organizations using GNU Emacs for Android may face compliance violations if exploited, potentially resulting in fines or legal consequences.

Mitigation Strategies

Update GNU Emacs for Android to the latest version that includes the patch for CVE-2026-71393. The fix prevents integer overflow in sfnt_read_name_table() by adding a check for the directory->length value before memory allocation.

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