BlackTreeCVE Intelligence
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Full vulnerability report · 2026
CVE-2026-117939High confidence

Use-after-free in the XML component

Mozilla · Firefox

6.3MediumCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 68 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.19% for the current model date.

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

  1. Confirm that the asset runs Mozilla Firefox and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 68 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-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.

11 package states
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 2 affected package states 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 releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcefirefox-esrVendor fix publishedDebian records a fixed source-package version for this release.153.6.0esr-1~deb13u1Debian Security Tracker ↗Source updated 4 Nov 2026
Debian trixietrixie · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:153.6.0esr-1~deb13u1Debian Security Tracker ↗Source updated 4 Nov 2026
Debian bookwormbookworm · sourcefirefox-esrVendor fix publishedDebian records a fixed source-package version for this release.153.6.0esr-1~deb12u2Debian Security Tracker ↗Source updated 4 Nov 2026
Debian bookwormbookworm · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:153.6.0esr-1~deb12u2Debian Security Tracker ↗Source updated 4 Nov 2026
Debian forkyforky · sourcefirefox-esrAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 4 Nov 2026
Debian forkyforky · sourcethunderbirdAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 4 Nov 2026
Debian sidsid · sourcefirefoxVendor fix publishedDebian records a fixed source-package version for this release.159.0-1Debian Security Tracker ↗Source updated 4 Nov 2026
Debian sidsid · sourcefirefox-esrVendor fix publishedDebian records a fixed source-package version for this release.153.6.0esr-1Debian Security Tracker ↗Source updated 4 Nov 2026
Debian sidsid · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:153.6.0esr-1Debian Security Tracker ↗Source updated 4 Nov 2026
Ubuntu 24.04 LTSnoble · standard archivemozjs102Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 4 Nov 2026
Ubuntu 24.04 LTSnoble · standard archivemozjs115Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 4 Nov 2026
Direct vendor intelligence

Authoritative 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.

1 current
CVE-2026-117939 · CSAF 2.0 · revision 3 · interimSUSE Product Security TeamCVE-2026-117939
66 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SUSE Linux Enterprise Desktop 15 SP7:MozillaFirefox
  • SUSE Linux Enterprise Desktop 15 SP7:MozillaFirefox-devel
  • SUSE Linux Enterprise Desktop 15 SP7:MozillaFirefox-translations-common
  • SUSE Linux Enterprise Desktop 15 SP7:MozillaFirefox-translations-other
  • SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS:MozillaFirefox
  • SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS:MozillaFirefox-devel
  • SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS:MozillaFirefox-translations-common
  • SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS:MozillaFirefox-translations-other
  • SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS:MozillaFirefox
  • SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS:MozillaFirefox-devel
  • SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS:MozillaFirefox-translations-common
  • SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS:MozillaFirefox-translations-other
Summary
Use-after-free in the XML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.
Remediation
No remediation text is recorded.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-110970

No EUVD known-exploited evidence

Use-after-free in the XML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
6.3 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 68 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

Use-after-free in the XML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

What

Use-after-free in the XML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Use-after-free in the XML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through a network path may attempt exploitation without authentication after a 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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

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 → Use After Free → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
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-416 ↗

CWE-416: Use After Free. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

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:R/S:U/C:L/I:L/A:L

Common 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.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.ILowIntegrity impact: A successful attack can cause a limited loss.ALowAvailability impact: A successful attack can cause a limited loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-416
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-110970Official EUVD mapping

Use-after-free in the XML component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

Official EUVD record ↗
BSI · German · WID-SEC-2026-4216Mozilla Firefox, Firefox ESR, und Thunderbird: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Mozilla Firefox, Mozilla Firefox ESR und Mozilla Thunderbird ausnutzen, um seine Privilegien zu erhöhen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Dateien zu manipulieren und um Sicherheitsvorkehrungen zu umgehen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1406Avis du CERT-FR

930 Référence CVE CVE-2026-117931 https://www.cve.org/CVERecord?id=CVE-2026-117931 Référence CVE CVE-2026-117932 https://www.cve.org/CVERecord?id=CVE-2026-117932 Référence CVE CVE-2026-117933 https://www.cve.org/CVERecord?id=CVE-2026-117933 Référence CVE CVE-2026-117934 https://www.cve.org/CVERecord?id=CVE-2026-117934 Référence CVE CVE-2026-117935 https://www.cve.org/CVERecord?id=CVE-2026-117935 Référence CVE CVE-2026-117936 https://www.cve.org/CVERecord?id=CVE-2026-117936 Référence CVE CVE-2026-117937 https://www.cve.org/CVERecord?id=CVE-2026-117937 Référence CVE CVE-2026-117938 https://www.cve.org/CVERecord?id=CVE-2026-117938 Référence CVE CVE-2026-117939 https://www.cve.org/CVERecord?id=CVE-2026-117939 Référence CVE CVE-2026-117940 https://www.cve.org/CVERecord?id=CVE-2026-117940 Référence CVE CVE-2026-117941 https://www.cve.org/CVERecord?id=CVE-2026-117941 Référence CVE CVE-2026-117942 https://www.cve.org/CVERecord?id=CVE-2026-117942 Référence CVE CVE-2026-117943 https://www.cve.org/CVERecord?id=CVE-2026-117943 Référence CVE CVE-2026-117944 https://www.cve.org/CVERecord?id=CVE-2026-117944 Référence CVE CVE-2026-117945 https://www.cve.org/CVERecord?id=CVE-2026-117945 Référence CVE CVE-2026-117946 https://www.cve.org/CVERecord?id=CVE-2026-117946 Référence CVE CVE-2026-117947 https://www.cve.o

Official advisory ↗
CSIRT Italia · Italian · risolte-vulnerabilita-in-prodotti-mozilla-14Risolte vulnerabilità in prodotti Mozilla

a - - CVE-2026-117953 : apre una nuova finestra - - CVE-2026-117952 : apre una nuova finestra - - CVE-2026-117951 : apre una nuova finestra - - CVE-2026-117950 : apre una nuova finestra - - CVE-2026-117949 : apre una nuova finestra - - CVE-2026-117948 : apre una nuova finestra - - CVE-2026-117947 : apre una nuova finestra - - CVE-2026-117946 : apre una nuova finestra - - CVE-2026-117945 : apre una nuova finestra - - CVE-2026-117944 : apre una nuova finestra - - CVE-2026-117943 : apre una nuova finestra - - CVE-2026-117942 : apre una nuova finestra - - CVE-2026-117941 : apre una nuova finestra - - CVE-2026-117940 : apre una nuova finestra - - CVE-2026-117939 : apre una nuova finestra - - CVE-2026-117938 : apre una nuova finestra - - CVE-2026-117937 : apre una nuova finestra - - CVE-2026-117936 : apre una nuova finestra - - CVE-2026-117935 : apre una nuova finestra - - CVE-2026-117934 : apre una nuova finestra - - CVE-2026-117933 : apre una nuova finestra - - CVE-2026-117932 : apre una nuova finestra - - CVE-2026-117931 : apre una nuova finestra - - CVE-2026-117930 : apre una nuova finestra - - CVE-2026-117929 : apre una nuova finestra - - CVE-2026-117928 : apre una nuova finestra - - CVE-2026-117927 : apre una nuova finestra - - CVE-2026-117926 : apre una nuova finestra - - CVE-2026-117925 : apr

Official advisory ↗
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
Fixed
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
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles5 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 Firefox 159 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 3 Nov 2026Security Vulnerabilities fixed in Firefox 159 Announced October 27, 2026 Impact high Products Firefox Fixed in Firefox 159 Note : We have changed how we publish advisories. We no longer roll all internally identified memory safety vulnerabilities into a single CVE and are now issuing an advisory for every indivi
  • Security Vulnerabilities fixed in Firefox ESR 115.44 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 3 Nov 2026Security Vulnerabilities fixed in Firefox ESR 115.44 Announced October 27, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 115.44 Note : We have changed how we publish advisories. We no longer roll all internally identified memory safety vulnerabilities into a single CVE and are now issuing an advisor
  • Security Vulnerabilities fixed in Firefox ESR 153.6 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 3 Nov 2026Security Vulnerabilities fixed in Firefox ESR 153.6 Announced October 27, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 153.6 Note : We have changed how we publish advisories. We no longer roll all internally identified memory safety vulnerabilities into a single CVE and are now issuing an advisory
  • 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, 19:40 UTC · CWE-416 · Use After Free

CVE recordCVE.org · 5.2
CVSS sourceCISA ADP
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-10-28
European sourceENISA EUVD · EUVD-2026-110970
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceCVE/CNA references
CWE sourceCISA ADP
NVD statusNVD not scheduled

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. SeveritySeverity changed from Unknown to Medium.
    Before
    Unknown
    After
    Medium
    CISA ADP ↗
  2. CVSS scoreCVSS score changed from not recorded to 6.3 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L).
    Before
    not recorded
    After
    6.3 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L)
    CISA ADP ↗
  3. ENISA EUVD mappingEUVD-2026-110970 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-110970"}
    ENISA EUVD ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: added remediation: bugzilla.mozilla.org/show_bug.cgi?id=2082030; removed remediation: mozilla.org/mfsa2026-121.
    Before
    remediation: mozilla.org/mfsa2026-121
    After
    remediation: bugzilla.mozilla.org/show_bug.cgi?id=2082030
    CNA ↗
  5. Vendor guidanceAuthoritative vendor guidance changed: added remediation: mozilla.org/mfsa2026-121; removed remediation: bugzilla.mozilla.org/show_bug.cgi?id=2082030.
    Before
    remediation: bugzilla.mozilla.org/show_bug.cgi?id=2082030
    After
    remediation: mozilla.org/mfsa2026-121
    CNA ↗
  6. Affected versionsThe structured affected or fixed version information changed.
    Before
    See the vendor and CVE records for the affected range. · Fixed: Firefox: 115.44 ≤ 115.*, 153.6 ≤ 153.*, 159 ≤ *
    After
    See the vendor and CVE records for the affected range. · Fixed: Firefox: 115.44 ≤ 115.*, 153.6 ≤ 153.*, 159 ≤ *; Thunderbird: 153.6 ≤ 153.*, 159 ≤ *
    CNA ↗
  7. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-110970↗Vendor CSAF · SUSE Product Security Team↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
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.
Free version - for non-commercial use only.CVE-2026-117939 · cve.blacktree.nl