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CVE-2026-71391

Off-by-One Error in GNU Emacs for Android

5.3 Medium

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

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
None

Exploit likelihood

0.54%Up 0.2 points since Aug 11, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.3

Off-by-One Error in GNU Emacs for Android

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

Record
CVE-2026-71391
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
Weakness
CWE-193
Updated
2026-11-02
EUVDEUVD-2026-55260 5.3

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

Record
EUVD-2026-55260
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-49vj-r7f8-c3p6 5.3

GNU Emacs for Android contains an off-by-one error in the gvar table parser in src/sfnt.c. The...

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

Record
GHSA-49vj-r7f8-c3p6
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-193
Updated
2026-11-02
NVD 5.3

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

Record
CVE-2026-71391
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-193
Updated
2026-11-02
OSV 5.3

Off-by-One Error in GNU Emacs for Android

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

Record
CVE-2026-71391
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
Weakness
CWE-193
Updated
2026-11-02
OSVDEBIAN-CVE-2026-71391 5.3

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

Record
DEBIAN-CVE-2026-71391
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Updated
2026-11-02
OSVUBUNTU-CVE-2026-71391 5.3

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

Record
UBUNTU-CVE-2026-71391
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
emacs24
Ubuntu:Pro:16.04:LTS
 All versions, plus listed versions
24.5+1-1ubuntu224.5+1-1ubuntu424.5+1-1ubuntu524.5+1-1ubuntu624.5+1-1ubuntu7
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24.5+1-6ubuntu124.5+1-6ubuntu1.124.5+1-6ubuntu1.1+esm124.5+1-6ubuntu1.1+esm224.5+1-6ubuntu1.1+esm324.5+1-6ubuntu1.1+esm4
 None known
xemacs21
Ubuntu:16.04:LTS
 All versions, plus listed versions
21.4.22-4ubuntu321.4.22-14ubuntu1
 None known
xemacs21-packages
Ubuntu:16.04:LTS
 All versions, plus listed versions
2009.02.17.dfsg.2-2
 None known
emacs25
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
25.2+1-625.2+1-6ubuntu0.1~esm2
 None known
xemacs21
Ubuntu:18.04:LTS
 All versions, plus listed versions
21.4.24-4ubuntu121.4.24-5ubuntu1
 None known
xemacs21-packages
Ubuntu:18.04:LTS
 All versions, plus listed versions
2009.02.17.dfsg.2-4
 None known
emacs
Ubuntu:Pro:20.04:LTS
 All versions, plus listed versions
1:26.3+1-1ubuntu11:26.3+1-1ubuntu21:26.3+1-1ubuntu2+esm11:26.3+1-1ubuntu2+esm2
 None known
xemacs21
Ubuntu:20.04:LTS
 All versions, plus listed versions
21.4.24-8build121.4.24-9
 None known
xemacs21-packages
Ubuntu:20.04:LTS
 All versions, plus listed versions
2009.02.17.dfsg.2-42009.02.17.dfsg.2-5
 None known
xemacs21
Ubuntu:22.04:LTS
 All versions, plus listed versions
21.4.24-9ubuntu2
 None known
Show 11 moreShow less
Affected packages
PackageAffectedFixed
xemacs21-packages
Ubuntu:22.04:LTS
 All versions, plus listed versions
2009.02.17.dfsg.2-5
 None known
emacs
Ubuntu:Pro:22.04:LTS
 All versions, plus listed versions
1:27.1+1-3ubuntu31:27.1+1-3ubuntu51:27.1+1-3ubuntu5.11:27.1+1-3ubuntu5.21:27.1+1-3ubuntu5.2+esm1
 None known
xemacs21
Ubuntu:24.04:LTS
 All versions, plus listed versions
21.4.24-1221.4.24-12build221.4.24-12build3
 None known
xemacs21-packages
Ubuntu:24.04:LTS
 All versions, plus listed versions
2009.02.17.dfsg.3-22009.02.17.dfsg.3-3
 None known
emacs
Ubuntu:Pro:24.04:LTS
 All versions, plus listed versions
1:29.1+1-5ubuntu11:29.2+1-1ubuntu11:29.2+1-2ubuntu41:29.3+1-1ubuntu21:29.3+1-1ubuntu2+esm11:29.3+1-1ubuntu2+esm31:29.3+1-1ubuntu2+esm4
 None known
emacs
Ubuntu:26.10
 All versions, plus listed versions
1:30.2+1-2ubuntu11:30.2+1-6ubuntu11:30.2+1-11ubuntu1
 None known
xemacs21
Ubuntu:26.10
 All versions, plus listed versions
21.4.24-12build3
 None known
xemacs21-packages
Ubuntu:26.10
 All versions, plus listed versions
2009.02.17.dfsg.3-3build1
 None known
xemacs21
Ubuntu:26.04:LTS
 All versions, plus listed versions
21.4.24-12build3
 None known
xemacs21-packages
Ubuntu:26.04:LTS
 All versions, plus listed versions
2009.02.17.dfsg.3-32009.02.17.dfsg.3-3build1
 None known
emacs
Ubuntu:Pro:26.04:LTS
 All versions, plus listed versions
1:30.1+1-9ubuntu11:30.2+1-1ubuntu21:30.2+1-2ubuntu11:30.2+1-2ubuntu1+esm1
 None known

History

History
RecordedChangedSources
affected
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-71391 is a medium vulnerability (CVSS 5.3) in Gnu Emacs, published August 10, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.54%, the 45th percentile. No source names a fixed version.

References

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