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

Quick assessment

Affected
GNU Emacs
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

GNU emacs是美国GNU基金会开源的一款可扩展的文本编辑环境。 GNU Emacs 30.2及之前版本存在数字错误漏洞，该漏洞源于src/sfnt.c中gvar表解析器存在差一错误，共享坐标索引边界检查使用严格大于比较而非大于等于，导致特制TrueType可变字体绕过检查并通过memcpy触发堆越界读取，攻击者可通过电子邮件、EWW或自定义字体的文档传递恶意字体文件，造成堆内存内容泄露，进而可用于绕过ASLR。

CVSS 5.3 · Medium EPSS 0.54% · P44

Affected Version Matrix 1

VendorProduct Version RangeStatus
GNU Emacs ≤ 30.2 affected
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I. Basic Information for CVE-2026-71391

Vulnerability Information
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Vulnerability Title
Off-by-One Error in GNU Emacs for Android
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
Off-by-one错误
Source: CVE Program / CVE List V5
Vulnerability Title
GNU Emacs 数字错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
GNU emacs是美国GNU基金会开源的一款可扩展的文本编辑环境。 GNU Emacs 30.2及之前版本存在数字错误漏洞，该漏洞源于src/sfnt.c中gvar表解析器存在差一错误，共享坐标索引边界检查使用严格大于比较而非大于等于，导致特制TrueType可变字体绕过检查并通过memcpy触发堆越界读取，攻击者可通过电子邮件、EWW或自定义字体的文档传递恶意字体文件，造成堆内存内容泄露，进而可用于绕过ASLR。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
GNU Emacs 0 ~ 30.2 -

II. Public POCs for CVE-2026-71391

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III. Intelligence Information for CVE-2026-71391

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Patches & Fixes for CVE-2026-71391 (1)

Security Blog Posts for CVE-2026-71391 (1)

Other References for CVE-2026-71391 (1)

Same Patch Batch · GNU · 2026-08-10 · 7 CVEs total

CVE-2026-71392 5.3 MEDIUM Integer Overflow in GNU Emacs for Android
CVE-2026-71393 5.3 MEDIUM Heap Buffer Overflow in GNU Emacs for Android
CVE-2026-71394 5.3 MEDIUM Heap Use of Uninitialized Memory in GNU Emacs for Android
CVE-2026-66484 4.6 MEDIUM Path Traversal in GNU cpio
CVE-2026-66486 4.6 MEDIUM Improper Output Encoding in GNU cpio
CVE-2026-66485 4.6 MEDIUM Uncontrolled Memory Allocation in GNU cpio

IV. Related Vulnerabilities

Same product: Emacs
Same vendor: GNU
Same weakness: CWE-193

V. Comments for CVE-2026-71391

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