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CVE Record

CVE-2026-12329: Memory safety bug fixed in Thunderbird ESR 140.12

Memory safety bug fixed in Thunderbird ESR 140.12. This vulnerability was fixed in Firefox ESR 140.12 and Thunderbird 140.12.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-12329 is a high-severity Mozilla memory safety issue fixed in Firefox ESR 140.12 and Thunderbird 140.12. A successful attack could affect confidentiality, integrity, and availability, but the CVSS vector requires user interaction and high attack complexity. The source bundle does not show active exploitation.

Executive priority

Treat this as a prompt patching item for managed browsers and mail clients, especially on user workstations. It is not currently supported as actively exploited in the provided sources, so prioritize remediation through normal high-severity endpoint update channels.

Technical view

The record maps to memory safety classes including out-of-bounds memory access, use-after-free, and null pointer dereference. CVSS 3.1 is 7.5 with network attack vector, no privileges required, user interaction required, high complexity, and high C/I/A impact. Mozilla and Red Hat advisories are the primary remediation sources.

Likely exposure

Exposure is most likely where Firefox ESR or Thunderbird deployments have not been updated to the fixed 140.12 releases or vendor-packaged equivalents. Red Hat references indicate downstream packages may also need vendor errata review.

Exploitation context

The bundle marks KEV as false and provides no cited evidence of active exploitation. The risk is still material because memory safety bugs in browser and mail-client components can become serious when users open hostile web or message content.

Researcher notes

Evidence is limited to advisory metadata and issue references; the bundle does not include exploit details or complete affected-version ranges. Validation should focus on vendor advisory mapping, package backport status, and whether scanners correctly recognize fixed downstream builds.

Mitigation direction

  • Update Firefox ESR and Thunderbird to fixed 140.12 releases or later.
  • Apply relevant Red Hat errata for downstream packaged versions.
  • Prioritize systems handling email, web browsing, or untrusted content.
  • Check Mozilla and distribution advisories for product-specific guidance.

Validation and detection

  • Inventory Firefox ESR and Thunderbird versions across managed endpoints.
  • Confirm installed versions include the 140.12 fixes or vendor backports.
  • Review Red Hat advisory applicability for subscribed systems.
  • Check vulnerability scanners for CVE-2026-12329 coverage and false positives.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-119: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-416: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-476: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-12329 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
19Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.65.9redhat-SADP
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-12329Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPfirefox: thunderbird: Memory safety bug fixed in Thunderbird ESR 140.12
other:Red Hat severity ratingcvssV3_1
  • 2026-06-16T14:01:19.195Z: Reported to Red Hat.
  • 2026-06-16T11:53:02.833Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox140.12Listed
MozillaThunderbird140.12Listed
Weakness

CWE details

CWE-119CWE-416CWE-476

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.