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CVE Record

CVE-2026-2760: Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component

Sandbox escape due to incorrect boundary conditions 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

This is a critical Mozilla browser and mail-client sandbox escape in Graphics: WebRender. A sandbox escape can let malicious content break out of the normal containment boundary. Mozilla states it is fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Executive priority

Prioritize remediation immediately for managed browsers and mail clients. There is no active-exploitation evidence in the supplied sources, but the combination of sandbox escape, network reachability, and CVSS 10.0 justifies urgent patching.

Technical view

CVE-2026-2760 is described as incorrect boundary conditions in Mozilla Graphics: WebRender, classified as CWE-1384. The CVSS 3.1 score is 10.0 with network attack vector, low complexity, no privileges, no user interaction, changed scope, and high confidentiality, integrity, and availability impact.

Likely exposure

Organizations with Mozilla Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR installations below the fixed releases are the primary concern. Red Hat references and errata indicate downstream package exposure may also matter for Red Hat environments.

Exploitation context

The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Public technical detail is limited, so do not assume exploit availability. The risk remains high because the issue is a sandbox escape with CVSS 10.0 severity.

Researcher notes

Focus validation on version and package state, not exploit reproduction. The bundle names WebRender boundary-condition handling but does not provide enough public detail to assess root cause, reachable code paths, or exploit primitives safely.

Mitigation direction

  • Update Firefox to Mozilla's fixed release channel version.
  • Update Firefox ESR to 115.33 or 140.8 where applicable.
  • Update Thunderbird to 148 or Thunderbird ESR to 140.8 where applicable.
  • Apply relevant Red Hat security errata for managed Linux packages.
  • Check Mozilla and vendor advisories for any environment-specific guidance.

Validation and detection

  • Inventory installed Firefox and Thunderbird versions across endpoints and servers.
  • Confirm ESR deployments are on the fixed ESR versions listed by Mozilla.
  • Review Red Hat advisory applicability for subscribed systems.
  • Verify software-management tools report successful update installation.
  • Monitor vendor advisories for revised affected-package status.
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-1384: 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-2026-2760 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: yesTechnical 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-2026-2760Attack 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 due to incorrect boundary conditions in the Graphics: WebRender component
other:Red Hat severity ratingcvssV3_1
  • 2026-02-24T14:04:36.459Z: Reported to Red Hat.
  • 2026-02-24T13:33:00.290Z: 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-1384

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

CWE-1384 · source CWE mapping

Improper Handling of Physical or Environmental Conditions

Improper Handling of Physical or Environmental Conditions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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