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Full vulnerability report · 2026
CVE-2026-12299High confidence

JIT miscompilation in the DOM: Core & HTML component

Mozilla · Firefox

5.4MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
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 0.31% 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.

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
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.140.12.0esr-1~deb13u1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian trixietrixie · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:140.12.0esr-1~deb13u1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcefirefox-esrVendor fix publishedDebian records a fixed source-package version for this release.140.12.0esr-1~deb12u1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:140.12.0esr-1~deb12u1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcefirefox-esrVendor fix publishedDebian records a fixed source-package version for this release.140.12.0esr-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:140.12.0esr-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcefirefoxVendor fix publishedDebian records a fixed source-package version for this release.152.0-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcefirefox-esrVendor fix publishedDebian records a fixed source-package version for this release.140.12.0esr-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcethunderbirdVendor fix publishedDebian records a fixed source-package version for this release.1:140.12.0esr-1Debian Security Tracker ↗Source updated 5 Oct 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 5 Oct 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 5 Oct 2026
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-2026-37090

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

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
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

What

JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

Why

The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

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

JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

Why

The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

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 → Access of Resource Using Incompatible Type ('Type Confusion') → 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-843 ↗

CWE-843: Access of Resource Using Incompatible Type ('Type Confusion'). The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

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:N

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.ANoneAvailability impact: No direct loss is represented by this metric.
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-843
A

Official authority intelligence

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

BSI · German · WID-SEC-2026-1959Mozilla Firefox, Firefox ESR und Thunderbird: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Mozilla Firefox, Mozilla Firefox ESR und Mozilla Thunderbird ausnutzen, um beliebigen Code auszuführen, erweiterte Berechtigungen zu erlangen, Speicherbeschädigungen zu verursachen, Sicherheitsmaßnahmen zu umgehen und aus der Sandbox auszubrechen, vertrauliche Informationen offenzulegen, Daten zu manipulieren und Denial-of-Service-Zustände auszulösen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0764Multiples vulnérabilités dans les produits Mozilla

d?id=CVE-2026-12290 Référence CVE CVE-2026-12291 https://www.cve.org/CVERecord?id=CVE-2026-12291 Référence CVE CVE-2026-12292 https://www.cve.org/CVERecord?id=CVE-2026-12292 Référence CVE CVE-2026-12293 https://www.cve.org/CVERecord?id=CVE-2026-12293 Référence CVE CVE-2026-12294 https://www.cve.org/CVERecord?id=CVE-2026-12294 Référence CVE CVE-2026-12295 https://www.cve.org/CVERecord?id=CVE-2026-12295 Référence CVE CVE-2026-12296 https://www.cve.org/CVERecord?id=CVE-2026-12296 Référence CVE CVE-2026-12297 https://www.cve.org/CVERecord?id=CVE-2026-12297 Référence CVE CVE-2026-12298 https://www.cve.org/CVERecord?id=CVE-2026-12298 Référence CVE CVE-2026-12299 https://www.cve.org/CVERecord?id=CVE-2026-12299 Référence CVE CVE-2026-12300 https://www.cve.org/CVERecord?id=CVE-2026-12300 Référence CVE CVE-2026-12301 https://www.cve.org/CVERecord?id=CVE-2026-12301 Référence CVE CVE-2026-12302 https://www.cve.org/CVERecord?id=CVE-2026-12302 Référence CVE CVE-2026-12303 https://www.cve.org/CVERecord?id=CVE-2026-12303 Référence CVE CVE-2026-12304 https://www.cve.org/CVERecord?id=CVE-2026-12304 Référence CVE CVE-2026-12305 https://www.cve.org/CVERecord?id=CVE-2026-12305 Référence CVE CVE-2026-12306 https://www.cve.org/CVERecord?id=CVE-2026-12306 Référence CVE CVE-2026-12307 https://www.cve.org/CVERecord?id=

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-019950Mozilla FoundationのMozilla Firefox等の複数製品における型の取り違えに関する脆弱性

DOM: CoreおよびHTMLコンポーネントにおけるJITミスコンパイルの脆弱性です。この脆弱性はFirefox 152、Firefox ESR 140.12、Firefox ESR 115.37、Thunderbird 152、およびThunderbird 140.12で修正されました。

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.
Patch available
Affected
See the vendor and CVE records for the affected range.
Fixed
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
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 articles10 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 152 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Firefox 152 Announced June 16, 2026 Impact high Products Firefox Fixed in Firefox 152 # CVE-2026-12289: Privilege escalation in the Graphics: WebRender component Reporter choeseyeong Impact high References Bug 2023443 # CVE-2026-12290: Memory safety bug fixed in Firefox 15
  • Security Vulnerabilities fixed in Thunderbird 152 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Thunderbird 152 Announced June 16, 2026 Impact high Products Thunderbird Fixed in Thunderbird 152 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or browser
  • Security Vulnerabilities fixed in Thunderbird 140.12 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Thunderbird 140.12 Announced June 16, 2026 Impact high Products Thunderbird Fixed in Thunderbird 140.12 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or b
  • Security Vulnerabilities fixed in Firefox ESR 140.12 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Firefox ESR 140.12 Announced June 16, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 140.12 # CVE-2026-12289: Privilege escalation in the Graphics: WebRender component Reporter choeseyeong Impact high References Bug 2023443 # CVE-2026-12290: Memory safety bug f
  • Security Vulnerabilities fixed in Firefox ESR 115.37 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Firefox ESR 115.37 Announced June 16, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 115.37 # CVE-2026-12289: Privilege escalation in the Graphics: WebRender component Reporter choeseyeong Impact high References Bug 2023443 # CVE-2026-12290: Memory safety bug f
  • Security Vulnerabilities fixed in Firefox 152 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Firefox 152 Announced June 16, 2026 Impact high Products Firefox Fixed in Firefox 152 # CVE-2026-12289: Privilege escalation in the Graphics: WebRender component Reporter choeseyeong Impact high References Bug 2023443 # CVE-2026-12290: Memory safety bug fixed in Firefox 15
  • Security Vulnerabilities fixed in Thunderbird 152 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Thunderbird 152 Announced June 16, 2026 Impact high Products Thunderbird Fixed in Thunderbird 152 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or browser
  • Security Vulnerabilities fixed in Thunderbird 140.12 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Thunderbird 140.12 Announced June 16, 2026 Impact high Products Thunderbird Fixed in Thunderbird 140.12 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or b
  • Security Vulnerabilities fixed in Firefox ESR 140.12 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Firefox ESR 140.12 Announced June 16, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 140.12 # CVE-2026-12289: Privilege escalation in the Graphics: WebRender component Reporter choeseyeong Impact high References Bug 2023443 # CVE-2026-12290: Memory safety bug f
  • Security Vulnerabilities fixed in Firefox ESR 115.37 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Security Vulnerabilities fixed in Firefox ESR 115.37 Announced June 16, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 115.37 # CVE-2026-12289: Privilege escalation in the Graphics: WebRender component Reporter choeseyeong Impact high References Bug 2023443 # CVE-2026-12290: Memory safety bug f
04

Evidence and provenance

Published 16 Jun 2026 · Last source change 15 Jul 2026, 11:48 UTC · CWE-843 · Access of Resource Using Incompatible Type ('Type Confusion')

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 2026-08-14
European sourceENISA EUVD · EUVD-2026-37090
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCISA ADP
NVD statusNVD modified after enrichment

Missing structured fields: affected versions. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

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-2026-37090↗Vendor advisory↗Vendor advisory↗Vendor advisory↗Vendor advisory↗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-2026-12299 · cve.blacktree.nl