CVE-2026-118176
Bypass of remote UNC path restriction in mailbox: URLs
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Bypass of remote UNC path restriction in mailbox: URLs
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
- Record
CVE-2026-118176- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-200
- Updated
- 2026-11-04
EUVDEUVD-2026-111353
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
- Record
EUVD-2026-111353- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-04
GitHub AdvisoriesGHSA-g4vf-4v95-x4pc
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network...
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
- Record
GHSA-g4vf-4v95-x4pc- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-200
- Updated
- 2026-11-04
NVD
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
- Record
CVE-2026-118176- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-200
- Updated
- 2026-11-04
OSVDEBIAN-CVE-2026-118176
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
- Record
DEBIAN-CVE-2026-118176- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-05
OSVUBUNTU-CVE-2026-118176
Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
- Record
UBUNTU-CVE-2026-118176- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-06
OSVopenSUSE-SU-2026:12339-1 No score
MozillaThunderbird-153.6.0-1.1 on GA media
These are all security issues fixed in the MozillaThunderbird-153.6.0-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:12339-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
thunderbirdDebian:12 |
before 1:153.6.0esr-1~deb12u2, plus listed versions 1:102.11.0-11:102.12.0-11:102.12.0-1~deb10u11:102.12.0-1~deb11u11:102.12.0-1~deb12u1 Show 45 moreShow less1:102.13.0-11:102.13.0-1~deb10u11:102.13.0-1~deb11u11:102.13.0-1~deb12u11:102.13.1-11:102.13.1-1~deb10u11:102.13.1-1~deb11u11:102.13.1-1~deb12u11:102.14.0-1~deb10u11:102.14.0-1~deb11u11:102.14.0-1~deb12u11:102.15.0-1~deb10u11:102.15.0-1~deb11u11:102.15.0-1~deb12u11:102.15.1-1~deb10u11:102.15.1-1~deb11u11:102.15.1-1~deb12u11:103.0~b5-11:104.0~b2-11:110.0~b4-11:112.0~b1-11:113.0~b3-11:114.0~b2-11:115.0-11:115.0.1-11:115.0.1-21:115.0~b4-11:115.0~b6-11:115.1.0-11:115.1.1-11:115.10.1-11:115.10.1-1~deb10u11:115.10.1-1~deb11u11:115.10.1-1~deb12u11:115.11.0-11:115.11.0-1~deb10u11:115.11.0-1~deb11u11:115.11.0-1~deb12u11:115.12.0-11:115.12.0-1~deb10u11:115.12.0-1~deb11u11:115.12.0-1~deb12u11:115.13.0-11:115.13.0-1~deb11u11:115.13.0-1~deb12u1 |
1:153.6.0esr-1~deb12u2 |
thunderbirdDebian:13 |
before 1:153.6.0esr-1~deb13u1, plus listed versions 1:128.13.0esr-11:128.14.0esr-11:128.14.0esr-1~deb11u11:128.14.0esr-1~deb12u11:128.14.0esr-1~deb13u1 Show 45 moreShow less1:129.0~b6-11:130.0~b3-11:132.0~b6-11:135.0-11:136.0-11:137.0-11:138.0-11:140.0.1esr-11:140.1.0esr-11:140.1.1esr-11:140.10.0esr-11:140.10.0esr-1~deb11u11:140.10.0esr-1~deb12u11:140.10.0esr-1~deb13u11:140.10.1esr-11:140.10.1esr-1~deb11u11:140.10.1esr-1~deb12u11:140.10.1esr-1~deb13u11:140.10.2esr-11:140.10.2esr-1~deb11u11:140.10.2esr-1~deb12u11:140.10.2esr-1~deb13u11:140.11.0esr-11:140.11.0esr-1~deb11u11:140.11.0esr-1~deb12u11:140.11.0esr-1~deb13u11:140.12.0esr-11:140.12.0esr-1~deb11u11:140.12.0esr-1~deb12u11:140.12.0esr-1~deb13u11:140.13.0esr-11:140.13.0esr-21:140.13.0esr-2~deb11u11:140.13.0esr-2~deb12u11:140.13.0esr-2~deb13u11:140.14.0esr-11:140.14.0esr-1~deb11u11:140.14.0esr-1~deb12u11:140.14.0esr-1~deb13u11:140.15.0esr-1~deb12u11:140.15.0esr-1~deb13u11:140.16.0esr-1~deb12u11:140.16.0esr-1~deb13u11:140.17.0esr-1~deb12u11:140.17.0esr-1~deb13u1 |
1:153.6.0esr-1~deb13u1 |
thunderbirdDebian:14 |
All versions, plus listed versions 1:128.13.0esr-11:128.14.0esr-11:128.14.0esr-1~deb11u11:128.14.0esr-1~deb12u11:128.14.0esr-1~deb13u1 Show 45 moreShow less1:129.0~b6-11:130.0~b3-11:132.0~b6-11:135.0-11:136.0-11:137.0-11:138.0-11:140.0.1esr-11:140.1.0esr-11:140.1.1esr-11:140.10.0esr-11:140.10.0esr-1~deb11u11:140.10.0esr-1~deb12u11:140.10.0esr-1~deb13u11:140.10.1esr-11:140.10.1esr-1~deb11u11:140.10.1esr-1~deb12u11:140.10.1esr-1~deb13u11:140.10.2esr-11:140.10.2esr-1~deb11u11:140.10.2esr-1~deb12u11:140.10.2esr-1~deb13u11:140.11.0esr-11:140.11.0esr-1~deb11u11:140.11.0esr-1~deb12u11:140.11.0esr-1~deb13u11:140.12.0esr-11:140.12.0esr-1~deb11u11:140.12.0esr-1~deb12u11:140.12.0esr-1~deb13u11:140.13.0esr-11:140.13.0esr-21:140.13.0esr-2~deb11u11:140.13.0esr-2~deb12u11:140.13.0esr-2~deb13u11:140.14.0esr-11:140.14.0esr-1~deb11u11:140.14.0esr-1~deb12u11:140.14.0esr-1~deb13u11:140.15.0esr-1~deb12u11:140.15.0esr-1~deb13u11:140.16.0esr-1~deb12u11:140.16.0esr-1~deb13u11:140.17.0esr-1~deb12u11:140.17.0esr-1~deb13u1 |
None known |
mozjs52Ubuntu:18.04:LTS |
All versions, plus listed versions 52.3.1-0ubuntu352.3.1-7fakesync152.8.1-0ubuntu0.18.04.152.9.1-0ubuntu0.18.04.1 |
None known |
mozjs38Ubuntu:18.04:LTS |
All versions, plus listed versions 38.8.0~repack1-0ubuntu138.8.0~repack1-0ubuntu338.8.0~repack1-0ubuntu4 |
None known |
mozjs68Ubuntu:20.04:LTS |
All versions, plus listed versions 68.5.0-1~fakesync68.5.0-2~fakesync68.6.0-168.6.0-1ubuntu1 |
None known |
mozjs52Ubuntu:20.04:LTS |
All versions, plus listed versions 52.9.1-1build152.9.1-1ubuntu3 |
None known |
mozjs102Ubuntu:22.04:LTS |
All versions, plus listed versions 102.11.0-0ubuntu0.22.04.1102.12.0-0ubuntu0.22.04.1102.13.0-0ubuntu0.22.04.1102.15.1-0ubuntu0.22.04.1 |
None known |
mozjs78Ubuntu:22.04:LTS |
All versions, plus listed versions 78.13.0-178.15.0-278.15.0-4ubuntu1 |
None known |
mozjs91Ubuntu:22.04:LTS |
All versions, plus listed versions 91.5.1-0ubuntu191.6.0-191.6.0-291.7.0-291.10.0-0ubuntu1 |
None known |
Show 4 moreShow less
| Package | Affected | Fixed |
|---|---|---|
thunderbirdUbuntu:22.04:LTS |
All versions, plus listed versions 1:91.1.2+build1-0ubuntu11:91.3.0+build2-0ubuntu11:91.3.1+build1-0ubuntu11:91.3.2+build1-0ubuntu11:91.4.0+build1.1-0ubuntu1 Show 34 moreShow less1:91.4.0+build2-0ubuntu11:91.5.0+build1-0ubuntu11:91.5.1+build1-0ubuntu11:91.6.1+build1-0ubuntu11:91.7.0+build1-0ubuntu11:91.7.0+build2-0ubuntu11:91.8.0+build2-0ubuntu11:91.9.1+build1-0ubuntu0.22.04.11:91.11.0+build2-0ubuntu0.22.04.11:102.2.2+build1-0ubuntu0.22.04.11:102.4.2+build2-0ubuntu0.22.04.11:102.7.1+build2-0ubuntu0.22.04.11:102.8.0+build2-0ubuntu0.22.04.11:102.9.0+build1-0ubuntu0.22.04.11:102.10.0+build2-0ubuntu0.22.04.11:102.11.0+build1-0ubuntu0.22.04.11:102.13.0+build1-0ubuntu0.22.04.11:102.15.0+build1-0ubuntu0.22.04.11:102.15.1+build1-0ubuntu0.22.04.11:115.3.1+build1-0ubuntu0.22.04.21:115.4.1+build1-0ubuntu0.22.04.11:115.5.0+build1-0ubuntu0.22.04.11:115.6.0+build2-0ubuntu0.22.04.11:115.8.1+build1-0ubuntu0.22.04.11:115.9.0+build1-0ubuntu0.22.04.11:115.10.1+build1-0ubuntu0.22.04.11:115.11.0+build2-0ubuntu0.22.04.11:115.12.0+build3-0ubuntu0.22.04.11:115.13.0+build5-0ubuntu0.22.04.11:115.15.0+build1-0ubuntu0.22.04.11:115.16.0+build2-0ubuntu0.22.04.11:115.18.0+build1-0ubuntu0.22.04.11:128.12.0+build1-0ubuntu0.22.04.11:140.7.1+build1-0ubuntu0.22.04.1 |
None known |
mozjs102Ubuntu:24.04:LTS |
All versions, plus listed versions 102.15.1-1102.15.1-3ubuntu2 |
None known |
mozjs115Ubuntu:24.04:LTS |
All versions, plus listed versions 115.3.0-0ubuntu1115.4.0-2115.5.0-1115.6.0-1115.7.0-4 Show 4 moreShow less115.8.0-1115.9.0-1115.9.0-1build1115.10.0-1 |
None known |
MozillaThunderbirdopenSUSE:Tumbleweed From an advisory covering 153 CVEs |
before 153.6.0-1.1 | 153.6.0-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | EUVD, GitHub Advisories, NVD, OSV | |
| cwes, facts, severity | CVE List | |
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-118176 is a high vulnerability (CVSS 8.1) in Mozilla Thunderbird, published October 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.40%, the 34th percentile. Fixed in thunderbird 1:153.6.0esr-1~deb12u2.
References
bugzilla.mozilla.org/show_bug.cgi?id=2081141
mozilla.org/security/advisories/mfsa2026-121
nvd.nist.gov/vuln/detail/CVE-2026-118176
github.com/advisories/GHSA-g4vf-4v95-x4pc
security-tracker.debian.org/tracker/CVE-2026-118176
Show 156 moreShow less
ubuntu.com/security/CVE-2026-118176
cve.org/CVERecord?id=CVE-2026-118176
suse.com/security/cve/CVE-2026-110247
Left out here: 321 versions. The JSON record has them.