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No exploitation reportedFix available

CVE-2026-118176

Bypass of remote UNC path restriction in mailbox: URLs

No exploitation reported by the sources we read.

  • Published2026-10-27
  • WeaknessCWE-200

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2026-10-2718:16CVE publishedCNA

Versions per branch

Products declared by the CNA1 product

As mozilla, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Mozilla Thunderbird

    Not affected ≥ 153.6, ≤ 153.* · ≥ 159

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-10-27

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • MozillaThunderbirdopenSUSE:Tumbleweedall versions · fixed in 153.6.0-1.1
  • mozjs102Ubuntu:24.04:LTSall versions · no fixed version listedand 1 other package
  • mozjs38Ubuntu:18.04:LTSall versions · no fixed version listedand 1 other package
  • mozjs52Ubuntu:20.04:LTSall versions · no fixed version listedand 1 other package
  • mozjs78Ubuntu:22.04:LTSall versions · no fixed version listedand 3 other packages
  • thunderbirdDebian:14all versions · no fixed version listed
  • thunderbirdDebian:13all versions · fixed in 1:153.6.0esr-1~deb13u1
  • thunderbirdDebian:12all versions · fixed in 1:153.6.0esr-1~deb12u2

Vendor advisories

  • CVE-2026-118176 Red Hat Product Security6 known affected

    thunderbird: Bypass of remote UNC path restriction in mailbox: URLs

    thunderbird as a component of Red Hat Enterprise Linux 10 · thunderbird.src as a component of Red Hat Enterprise Linux 10 · thunderbird as a component of Red Hat Enterprise Linux 8 · +3 more

Full record on NVD

Fix

  1. Workaround from the vendor Red Hat Product Security CVE-2026-118176 · 6 products--- CME Mitigation Guidance (2026-11-03) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to indepen…
  2. No fix available, says the vendor Red Hat Product Security CVE-2026-118176 · 6 productsFix deferred

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Published
2026-10-27
Last Modified
2026-11-04
NVD status
Deferred
GitHub Advisory
GHSA-g4vf-4v95-x4pc

Frequently asked questions

What is 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.

Is CVE-2026-118176 actively exploited?

Active exploitation of CVE-2026-118176 has not been confirmed. Its EPSS score was 0.2% on 2026-11-04, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-118176?

CVE-2026-118176 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.

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