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.
CVE-2026-118176
UNRATEDCVSS · not yet scoredTrending — 6 sources updated this week
Also known asEUVD-2026-111353 (ENISA EUVD) · GHSA-g4vf-4v95-x4pc (GitHub Security Advisories)Source: ENISA EUVD
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EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- No CVSS published and no exploitation signals yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS v2: —Exploit: None knownExposed services: Not assessed
The CVE record names the fixed release — apply it.
- CVSS v3
- —
- EchelonGraph score
- Not yet assessedNo source has published severity data for this CVE yet — no CVSS score from NVD or a CNA, no GitHub advisory, and it is not in CISA KEV. This is not a rating of zero; we cannot assess it yet.
- EG Score
- —
- EG Risk
- —
- EPSS PROB
- 0.2%
- EPSS %ILE
- 12th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- No SSVC decision: EchelonGraph has not assessed this CVECISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the BOD 26-04 block below.
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
October 27, 2026
Last Modified
October 28, 2026
References (3)
- security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=2081141
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-121/
- security@mozillahttps://www.mozilla.org/security/advisories/mfsa2026-122/
Vendor Advisories for CVE-2026-118176(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Data Freshness Timeline
(refreshed 11× in last 7d / 11× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
- 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.2% · 12th percentile
- 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
- 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
- 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
- 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.2% · 12th percentile
- 2026-10-28 14:50 UTCGHSA enrichmentGHSA-g4vf-4v95-x4pc
- 2026-10-27 19:26 UTCNVD update
- 2026-10-27 19:01 UTCENISA EUVD ID recordedEUVD-2026-111353 · Source: ENISA EUVD
- 2026-10-27 18:20 UTCEG score recompute
- 2026-10-27 18:19 UTCMITRE cvelistV5first tracked
Frequently asked(4)
What is CVE-2026-118176?
CVE-2026-118176 is a vulnerability whose severity is not yet rated; its CVE record was published on October 27, 2026. 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…
When was the CVE record for CVE-2026-118176 published?
The CVE record for CVE-2026-118176 was published on October 27, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 28, 2026; the record at its source may have been updated since.
Is CVE-2026-118176 actively exploited?
CVE-2026-118176 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (12th percentile of EPSS-scored CVEs).
How do I remediate CVE-2026-118176?
The CVE record for CVE-2026-118176 names the fix: "This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6." The vendor advisories EchelonGraph has for CVE-2026-118176 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-118176
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