Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.19% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-117887High confidence
Use-after-free in the DOM: Core & HTML component
Mozilla · Firefox
8.8HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 91 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 severityHigh→Operational priority:High, 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 Firefox 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 91 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Red Hat Product Security: 23 affected or under-investigation product states without a fixed product state in the same current advisory
- SUSE Product Security Team: 66 affected or under-investigation product states without a fixed product state in the same current advisory
- Debian Security Tracker: 2 affected package states with no published fix
Distribution package intelligence
11 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 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 release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | firefox-esr | Vendor fix publishedDebian records a fixed source-package version for this release. | 153.6.0esr-1~deb13u1 | Debian Security Tracker ↗Source updated 4 Nov 2026 |
| 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 | firefox-esr | Vendor fix publishedDebian records a fixed source-package version for this release. | 153.6.0esr-1~deb12u2 | 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 | firefox-esr | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | 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 | firefox | Vendor fix publishedDebian records a fixed source-package version for this release. | 159.0-1 | Debian Security Tracker ↗Source updated 4 Nov 2026 |
| Debian sidsid · source | firefox-esr | Vendor fix publishedDebian records a fixed source-package version for this release. | 153.6.0esr-1 | 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
2 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-2026-117887 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityfirefox: thunderbird: Use-after-free in the DOM: Core & HTML component
The vendor explicitly identifies these products as affected by this CVE.
- firefox as a component of Red Hat Enterprise Linux 10
- firefox.src as a component of Red Hat Enterprise Linux 10
- rhel10/firefox-flatpak as a component of Red Hat Enterprise Linux 10
- 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
- firefox as a component of Red Hat Enterprise Linux 6
- firefox.src as a component of Red Hat Enterprise Linux 6
- thunderbird as a component of Red Hat Enterprise Linux 6
- thunderbird.src as a component of Red Hat Enterprise Linux 6
- firefox as a component of Red Hat Enterprise Linux 7
- firefox.src as a component of Red Hat Enterprise Linux 7
- Summary
- A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Use-after-free in the DOM: Core & HTML component
- Remediation
- --- CME Mitigation Guidance (2026-11-02) --- 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 prevent execution against dangling DOM pointers by isolating or blocking untrusted DOM and HTML rendering in Firefox: upgrade to Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which corrects memory management and object lifecycle handling in the DOM: Core & HTML component to prevent use-after-free conditions, closing all 2 injection vectors (crafted web page, crafted HTML document). Until patched, this is a concern on Users processing untrusted web content or viewing untrusted HTML documents across all supported platforms, so Prevent users from visiting untrusted websites or opening unverified HTML documents in the browser. As a compensating measure, Maintain ASLR to randomize browser memory layout, making reliable code execution via dangling DOM pointers significantly harder, Enforce Full RELRO and PIE to keep binary segments and GOT entries randomized and read-only, impeding control-flow hijacking, and Operate SELinux in enforcing mode to confine the browser process and limit lateral movement or system access if exploitation occurs. These controls limit blast radius and contain exploitation, but they do not fix the underlying use-after-free defect — apply the upstream patch to fully remediate. Highest-impact CME: CME-301 SELinux (Enforcing Mode) (medium)
CVE-2026-117887 · CSAF 2.0 · revision 3 · interimSUSE Product Security TeamCVE-2026-117887
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 DOM: Core & HTML 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.
High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 91 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
Use-after-free in the DOM: Core & HTML 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 DOM: Core & HTML 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 DOM: Core & HTML 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 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 → 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:H/I:H/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.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major 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.
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
- firefox as a component of Red Hat Enterprise Linux 10
- firefox.src as a component of Red Hat Enterprise Linux 10
- rhel10/firefox-flatpak as a component of Red Hat Enterprise Linux 10
- 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
- firefox as a component of Red Hat Enterprise Linux 6
- firefox.src as a component of Red Hat Enterprise Linux 6
- thunderbird as a component of Red Hat Enterprise Linux 6
- thunderbird.src as a component of Red Hat Enterprise Linux 6
- firefox as a component of Red Hat Enterprise Linux 7
- firefox.src as a component of Red Hat Enterprise Linux 7
- thunderbird as a component of Red Hat Enterprise Linux 7
- thunderbird.src as a component of Red Hat Enterprise Linux 7
- firefox as a component of Red Hat Enterprise Linux 8
- firefox.src as a component of Red Hat Enterprise Linux 8
- thunderbird as a component of Red Hat Enterprise Linux 8
- thunderbird.src as a component of Red Hat Enterprise Linux 8
- firefox as a component of Red Hat Enterprise Linux 9
- firefox-x11 as a component of Red Hat Enterprise Linux 9
- firefox.src as a component of Red Hat Enterprise Linux 9
- 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 (2026-11-02) --- 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 prevent execution against dangling DOM pointers by isolating or blocking untrusted DOM and HTML rendering in Firefox: upgrade to Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6 (or the corresponding fixed Red Hat builds), which corrects memory management and object lifecycle handling in the DOM: Core & HTML component to prevent use-after-free conditions, closing all 2 injection vectors (crafted web page, crafted HTML document). Until patched, this is a concern on Users processing untrusted web content or viewing untrusted HTML documents across all supported platforms, so Prevent users from visiting untrusted websites or opening unverified HTML documents in the browser. As a compensating measure, Maintain ASLR to randomize browser memory layout, making reliable code execution via dangling DOM pointers significantly harder, Enforce Full RELRO and PIE to keep binary segments and GOT entries randomized and read-only, impeding control-flow hijacking, and Operate SELinux in enforcing mode to confine the browser process and limit lateral movement or system access if exploitation occurs. These controls limit blast radius and contain exploitation, but they do not fix the underlying use-after-free defect — apply the upstream patch to fully remediate. Highest-impact CME: CME-301 SELinux (Enforcing Mode) (medium)
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, 19:33 UTC · CWE-416 · Use After Free
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-2026-111058
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
- SeveritySeverity changed from Unknown to High.CISA ADP ↗
- Before
- Unknown
- After
- High
- CVSS scoreCVSS score changed from not recorded to 8.8 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).CISA ADP ↗
- Before
- not recorded
- After
- 8.8 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H)
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-117887 to remediation: access.redhat.com/CVE-2026-117887.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-117887
- After
- remediation: access.redhat.com/CVE-2026-117887
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Mitigation available
- ENISA EUVD mappingEUVD-2026-111058 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2026-111058"}
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: bugzilla.mozilla.org/show_bug.cgi?id=2077385; removed remediation: mozilla.org/mfsa2026-121.CNA ↗
- Before
- remediation: mozilla.org/mfsa2026-121
- After
- remediation: bugzilla.mozilla.org/show_bug.cgi?id=2077385
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: mozilla.org/mfsa2026-121; removed remediation: bugzilla.mozilla.org/show_bug.cgi?id=2077385.CNA ↗
- Before
- remediation: bugzilla.mozilla.org/show_bug.cgi?id=2077385
- After
- remediation: mozilla.org/mfsa2026-121
- Affected versionsThe structured affected or fixed version information changed.CNA ↗
- 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 ≤ *
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
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.