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CVE Record

CVE-2026-2761: Sandbox escape in the Graphics: WebRender component

Sandbox escape in the Graphics: WebRender component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

CriticalCVSS 10Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-2761 is a critical Mozilla sandbox escape in Graphics: WebRender. If present, it could let an attacker break out of a browser or mail client sandbox and affect confidentiality, integrity, and availability. Mozilla says it is fixed in current Firefox, ESR, and Thunderbird releases named in the advisories.

Executive priority

Treat this as urgent patching for affected browser and mail-client fleets. No active exploitation is proven in the supplied sources, but the impact rating and sandbox-escape class justify accelerated remediation and management visibility.

Technical view

The issue is classified as CWE-693 and scored CVSS 10.0 with network attack vector, low complexity, no privileges, no user interaction, changed scope, and high impact. The public bundle identifies WebRender sandbox escape behavior but does not provide detailed root-cause or exploit mechanics.

Likely exposure

Exposure is most likely where Mozilla Firefox or Thunderbird, including Red Hat-packaged builds, remain below the fixed releases: Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, or Thunderbird 140.8.

Exploitation context

The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Risk remains high because the CVSS vector describes remote, low-complexity exploitation with no privileges or user interaction, and complete confidentiality, integrity, and availability impact.

Researcher notes

Public detail is limited to advisory-level information. Avoid assuming a specific trigger or exploit chain. Focus validation on installed product versions, downstream package status, and whether vendor errata for CVE-2026-2761 have been applied.

Mitigation direction

  • Update Firefox to 148 or the supported ESR fixed release.
  • Update Thunderbird to 148 or 140.8, as applicable.
  • Apply relevant Red Hat security errata for packaged Mozilla components.
  • Check Mozilla and OS vendor advisories for deployment-specific guidance.
  • Prioritize managed endpoints and shared systems with browser or mail client exposure.

Validation and detection

  • Inventory installed Firefox and Thunderbird versions across endpoints and servers.
  • Confirm versions meet or exceed the Mozilla fixed releases.
  • Check Red Hat advisory applicability for affected packages in your environment.
  • Review vulnerability scanner results for CVE-2026-2761 after patching.
  • Verify software update policies cover ESR and Thunderbird channels.
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-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.

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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.

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cve · low confidence lookup

CVE-2026-2761 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
Critical
CVSS
10 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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
35Source 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
10CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H3.96CISA-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

10Critical
CVSS 3.1 vector shape for CVE-2026-2761Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 Graphics: WebRender component
other:Red Hat severity ratingcvssV3_1
  • 2026-02-24T14:03:35.826Z: Reported to Red Hat.
  • 2026-02-24T13:33:01.011Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.33, 140.8, 148Listed
MozillaThunderbird140.8, 148Listed
Weakness

CWE details

CWE-693

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

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.

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