Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 0.18% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-118177High confidence
Calendar discovery accepted local file and remote network share locations
Mozilla · Thunderbird
9.1CriticalCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productCritical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 10 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityCritical→Operational priority:Critical, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Mozilla Thunderbird and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 10 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Red Hat Product Security: 9 affected or under-investigation product states without a fixed product state in the same current advisory
- Debian Security Tracker: 1 affected package state with no published fix
Distribution package intelligence
6 package statesRelease-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Package result overrides the generic status
BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 1 affected package state shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | thunderbird | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:153.6.0esr-1~deb13u1 | Debian Security Tracker ↗Source updated 4 Nov 2026 |
| Debian bookwormbookworm · source | thunderbird | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:153.6.0esr-1~deb12u2 | Debian Security Tracker ↗Source updated 4 Nov 2026 |
| Debian forkyforky · source | thunderbird | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 4 Nov 2026 |
| Debian sidsid · source | thunderbird | Vendor fix publishedDebian records a fixed source-package version for this release. | 1:153.6.0esr-1 | Debian Security Tracker ↗Source updated 4 Nov 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | mozjs102 | Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 4 Nov 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | mozjs115 | Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 4 Nov 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2026-118177 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitythunderbird: Calendar discovery accepted local file and remote network share locations
The vendor explicitly identifies these products as affected by this CVE.
- thunderbird.src as a component of Red Hat Enterprise Linux 10
- thunderbird as a component of Red Hat Enterprise Linux 6
- thunderbird.src as a component of Red Hat Enterprise Linux 6
- thunderbird as a component of Red Hat Enterprise Linux 7
- thunderbird.src as a component of Red Hat Enterprise Linux 7
- thunderbird as a component of Red Hat Enterprise Linux 8
- thunderbird.src as a component of Red Hat Enterprise Linux 8
- thunderbird as a component of Red Hat Enterprise Linux 9
- thunderbird.src as a component of Red Hat Enterprise Linux 9
- Summary
- A flaw was found in Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file.
- Remediation
- --- 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 independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to reject calendar discovery URLs pointing to local file paths, network shares, or external servers during Thunderbird calendar setup: upgrade to Thunderbird 159 and Thunderbird 153.6 (or the fixed Thunderbird/Rhel10/Thunderbird Flatpak builds), which reject calendar discovery locations pointing to local files, network shares, or unauthorized remote servers, closing all 3 injection vectors (remote network share URL injection, local file path subscription injection, external server calendar redirection). Until patched, this is a concern on Thunderbird clients performing account setup or adding network calendars across all supported platforms, so Avoid configuring accounts or adding network calendars over unencrypted HTTP, and avoid connecting to untrusted calendar directory servers until the software is updated. As a compensating measure, Confine Thunderbird filesystem access boundaries to prevent the application from reading or overwriting arbitrary local files when subscribing to calendars and Enforce strict allowlist validation on calendar discovery URL schemes and endpoints, denying local file or UNC network locations by default. These controls limit blast radius and contain exploitation, but they do not fix the underlying calendar discovery path validation defect — apply the upstream patch to fully remediate. Highest-impact CME: CME-1301 Path Traversal Prevention (Canonicalization) (high)
Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 10 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
What
When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
Why
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.
Why
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → URL Redirection to Untrusted Site ('Open Redirect') → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-601 ↗
CWE-601: URL Redirection to Untrusted Site ('Open Redirect'). The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Affected
- thunderbird.src as a component of Red Hat Enterprise Linux 10
- thunderbird as a component of Red Hat Enterprise Linux 6
- thunderbird.src as a component of Red Hat Enterprise Linux 6
- thunderbird as a component of Red Hat Enterprise Linux 7
- thunderbird.src as a component of Red Hat Enterprise Linux 7
- thunderbird as a component of Red Hat Enterprise Linux 8
- thunderbird.src as a component of Red Hat Enterprise Linux 8
- thunderbird as a component of Red Hat Enterprise Linux 9
- thunderbird.src as a component of Red Hat Enterprise Linux 9
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- --- 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 independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to reject calendar discovery URLs pointing to local file paths, network shares, or external servers during Thunderbird calendar setup: upgrade to Thunderbird 159 and Thunderbird 153.6 (or the fixed Thunderbird/Rhel10/Thunderbird Flatpak builds), which reject calendar discovery locations pointing to local files, network shares, or unauthorized remote servers, closing all 3 injection vectors (remote network share URL injection, local file path subscription injection, external server calendar redirection). Until patched, this is a concern on Thunderbird clients performing account setup or adding network calendars across all supported platforms, so Avoid configuring accounts or adding network calendars over unencrypted HTTP, and avoid connecting to untrusted calendar directory servers until the software is updated. As a compensating measure, Confine Thunderbird filesystem access boundaries to prevent the application from reading or overwriting arbitrary local files when subscribing to calendars and Enforce strict allowlist validation on calendar discovery URL schemes and endpoints, denying local file or UNC network locations by default. These controls limit blast radius and contain exploitation, but they do not fix the underlying calendar discovery path validation defect — apply the upstream patch to fully remediate. Highest-impact CME: CME-1301 Path Traversal Prevention (Canonicalization) (high)
Official vendor articles2 stored documents
Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.
- Security Vulnerabilities fixed in Thunderbird 159 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 3 Nov 2026Security Vulnerabilities fixed in Thunderbird 159 Announced October 27, 2026 Impact high Products Thunderbird Fixed in Thunderbird 159 Many of these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, however they may pose risks in browser or browse
- Security Vulnerabilities fixed in Thunderbird 153.6 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 3 Nov 2026Security Vulnerabilities fixed in Thunderbird 153.6 Announced October 27, 2026 Impact high Products Thunderbird Fixed in Thunderbird 153.6 Many of these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, however they may pose risks in browser or br
04
Evidence and provenance
Published 27 Oct 2026 · Last source change 4 Nov 2026, 16:46 UTC · CWE-601 · URL Redirection to Untrusted Site ('Open Redirect')
CVE recordCVE.org · 5.2
CVSS sourceCISA ADP
EPSS source FIRST · tracked since 2026-10-28
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-111354
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCISA ADP
NVD statusNVD not scheduled
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- 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 6; thunderbird.src as a component of Red Hat Enterprise Linux 6; thunderbird as a component of Red Hat Enterprise Linux 7; thunderbird.src as a component of Red Hat Enterprise Linux 7; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 9; thunderbird.src as a component of Red Hat Enterprise Linux 9
- After
- thunderbird.src as a component of Red Hat Enterprise Linux 10; thunderbird as a component of Red Hat Enterprise Linux 6; thunderbird.src as a component of Red Hat Enterprise Linux 6; thunderbird as a component of Red Hat Enterprise Linux 7; thunderbird.src as a component of Red Hat Enterprise Linux 7; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 9; thunderbird.src as a component of Red Hat Enterprise Linux 9
- SeveritySeverity changed from Unknown to Critical.CISA ADP ↗
- Before
- Unknown
- After
- Critical
- CVSS scoreCVSS score changed from not recorded to 9.1 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H).CISA ADP ↗
- Before
- not recorded
- After
- 9.1 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H)
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-118177 to remediation: access.redhat.com/CVE-2026-118177.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-118177
- After
- remediation: access.redhat.com/CVE-2026-118177
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Mitigation available
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- rhel10/thunderbird-flatpak as a component of Red Hat Enterprise Linux 10; 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 6; thunderbird.src as a component of Red Hat Enterprise Linux 6; thunderbird as a component of Red Hat Enterprise Linux 7; thunderbird.src as a component of Red Hat Enterprise Linux 7; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 9; thunderbird.src as a component of Red Hat Enterprise Linux 9
- After
- 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 6; thunderbird.src as a component of Red Hat Enterprise Linux 6; thunderbird as a component of Red Hat Enterprise Linux 7; thunderbird.src as a component of Red Hat Enterprise Linux 7; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 9; thunderbird.src as a component of Red Hat Enterprise Linux 9
- BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.BlackTree editorial ↗
- Before
- no BlackTree article
- After
- 1 BlackTree article
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- 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; thunderbird.src as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 9; thunderbird.src as a component of Red Hat Enterprise Linux 9
- After
- rhel10/thunderbird-flatpak as a component of Red Hat Enterprise Linux 10; 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 6; thunderbird.src as a component of Red Hat Enterprise Linux 6; thunderbird as a component of Red Hat Enterprise Linux 7; thunderbird.src as a component of Red Hat Enterprise Linux 7; thunderbird as a component of Red Hat Enterprise Linux 8; thunderbird.src as a component of Red Hat Enterprise Linux 8; thunderbird as a component of Red Hat Enterprise Linux 9; thunderbird.src as a component of Red Hat Enterprise Linux 9
- ENISA EUVD mappingEUVD-2026-111354 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2026-111354"}
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: bugzilla.mozilla.org/show_bug.cgi?id=2080924; removed patch: mozilla.org/mfsa2026-121; removed patch: mozilla.org/mfsa2026-122; 1 further removals.CNA ↗
- Before
- patch: mozilla.org/mfsa2026-121 · patch: mozilla.org/mfsa2026-122 · remediation: mozilla.org/mfsa2026-122
- After
- remediation: bugzilla.mozilla.org/show_bug.cgi?id=2080924
- Affected versionsThe structured affected or fixed version information changed.CNA ↗
- Before
- See the linked Mozilla advisory for the product-specific affected versions. · Fixed: Thunderbird 153.6; Thunderbird 159
- After
- See the vendor and CVE records for the affected range. · Fixed: Thunderbird: 153.6 ≤ 153.*, 159 ≤ *
- SeveritySeverity changed from High to Unknown.CVE.org ↗
- Before
- High
- After
- Unknown
- Catalogue recordCVE added to the BlackTree catalogue.Authoritative vendor security advisory ↗
CVE published
Fixed release or patch reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.