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CVE Record

CVE-2026-12296: Sandbox escape in the Security: Process Sandboxing component

Sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

CriticalCVSS 9.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-12296 is a critical Mozilla sandbox-escape vulnerability. A successful attack could let browser or mail content break out of an intended security boundary, increasing the impact of other compromise paths. Mozilla states it was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

Executive priority

Treat as urgent for fleets using Mozilla browser or mail clients. The issue is critical, affects a security boundary, and has fixed releases available. Prioritize managed endpoint patching and vendor package updates, especially where users browse the web or open untrusted mail content.

Technical view

The issue is in Mozilla's Security: Process Sandboxing component and is classified as CWE-403 and CWE-693. CVSS 3.1 is 9.6 with network attack vector, low complexity, no privileges required, user interaction required, changed scope, and high confidentiality, integrity, and availability impact.

Likely exposure

Exposure is most likely on endpoints or servers running Firefox, Firefox ESR, or Thunderbird that have not reached Mozilla's fixed releases. Red Hat users should also check the linked Red Hat CVE, VEX, and RHSA entries for package-specific status.

Exploitation context

The supplied sources do not show CISA KEV listing or confirmed active exploitation. The CVSS vector indicates exploitation requires user interaction but no prior privileges, and impact is severe because a sandbox escape can weaken a core containment boundary.

Researcher notes

Evidence is limited to public advisories and CVE metadata in the supplied bundle. Bug details may be restricted. Do not assume exploit availability. Focus validation on fixed-version presence, OS package errata, and whether sandboxing exposure exists in deployed Mozilla products.

Mitigation direction

  • Update Firefox to version 152 or later where applicable.
  • Update Firefox ESR to version 140.12 or later.
  • Update Thunderbird to version 152 or 140.12 where applicable.
  • Apply relevant Red Hat security errata for managed Red Hat systems.
  • Check Mozilla and OS vendor advisories for product-specific guidance.

Validation and detection

  • Inventory installed Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm deployed versions meet or exceed the fixed releases named by Mozilla.
  • Review Red Hat package status if Mozilla packages are OS-managed.
  • Check vulnerability scanners for CVE-2026-12296 coverage and false positives.
  • Verify browser and mail auto-update policies are functioning.
Prepared
Confidence
high
Sources
10

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-403: 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-693: 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
description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-12296 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
Critical
CVSS
9.6 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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
21Source 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
9.6CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H2.86CISA-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

9.6Critical
CVSS 3.1 vector shape for CVE-2026-12296Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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: Sandbox escape in the Security: Process Sandboxing component
other:Red Hat severity ratingcvssV3_1
  • 2026-06-16T14:02:09.995Z: Reported to Red Hat.
  • 2026-06-16T11:52:29.869Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox140.12, 152Listed
MozillaThunderbird140.12, 152Listed
Weakness

CWE details

CWE-403CWE-693

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

CWE-403 · source CWE mapping

Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak')

Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-693 · source CWE mapping

Protection Mechanism Failure

Protection Mechanism Failure represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs