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CVE Record

CVE-2026-12291: Use-after-free in the Networking: HTTP component

Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-12291 is a high-severity memory safety flaw in Mozilla's HTTP networking code. A successful attack could let hostile web or message content compromise confidentiality, integrity, and availability, but the source bundle indicates user interaction is required. Mozilla lists fixes in Firefox 152, Firefox ESR 140.12/115.37, Thunderbird 152, and Thunderbird 140.12.

Executive priority

Patch in the next regular emergency browser/mail-client cycle, especially for enterprise desktops and ESR fleets. The severity is high because compromise impact is broad, but the provided evidence does not support calling this actively exploited.

Technical view

The issue is a use-after-free in Networking: HTTP, mapped to CWE-416 and CWE-825. CVSS 3.1 is 8.8 with AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. The bundle names Mozilla Firefox and Thunderbird and Red Hat downstream advisories, but gives no exploit mechanics or proof-of-concept details.

Likely exposure

Exposure is most likely on endpoints or servers running Firefox or Thunderbird before the fixed Mozilla releases, including managed ESR deployments and downstream Red Hat packages covered by the listed errata. Confirm actual installed package versions rather than relying on product presence alone.

Exploitation context

The bundle does not show CISA KEV listing and provides no cited evidence of active exploitation. The CVSS vector indicates network-delivered attack potential with low attack complexity, no privileges, and required user interaction. Treat this as urgent browser and mail-client patching, not confirmed in-the-wild exploitation.

Researcher notes

The public bundle is sparse: it identifies component, weakness class, CVSS, fixed versions, and vendor advisories, but not root-cause detail. Avoid assuming affected version ranges beyond releases older than Mozilla's named fixed versions unless vendor advisories confirm them.

Mitigation direction

  • Upgrade Firefox to 152 or applicable ESR 140.12/115.37.
  • Upgrade Thunderbird to 152 or ESR 140.12.
  • Apply relevant Red Hat RHSA packages where Mozilla components are vendor-managed.
  • Prioritize managed endpoints with default browsers, mail clients, or untrusted content exposure.
  • Check Mozilla and distribution advisories for any later superseding guidance.

Validation and detection

  • Inventory Firefox and Thunderbird versions across endpoints and server images.
  • Verify ESR channels meet Firefox ESR 140.12 or 115.37 as applicable.
  • Confirm Thunderbird installations meet 152 or 140.12.
  • Review Red Hat package status against the listed RHSA advisories.
  • Document exceptions where the product is absent or not reachable by users.
Prepared
Confidence
high
Sources
11

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-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.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-825: 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-2026-12291 mapping review

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

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/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
22Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

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
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9CISA-ADP
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

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2026-12291Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/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: Use-after-free in the Networking: HTTP component
other:Red Hat severity ratingcvssV3_1
  • 2026-06-16T14:02:52.191Z: Reported to Red Hat.
  • 2026-06-16T11:52:24.990Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.37, 140.12, 152Listed
MozillaThunderbird140.12, 152Listed
Weakness

CWE details

CWE-416CWE-825

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

CWE-416 · source CWE mapping

Use After Free

Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-825 · source CWE mapping

Expired Pointer Dereference

Expired Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs