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CVE Record

CVE-2026-0879: Sandbox escape due to incorrect boundary conditions in the Graphics component

Sandbox escape due to incorrect boundary conditions in the Graphics component. This vulnerability was fixed in Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-0879 is a critical Mozilla graphics vulnerability that could allow escape from a sandbox boundary. For executives, the urgency is browser and mail-client fleet hygiene: systems using unfixed Firefox or Thunderbird builds should be updated promptly because the assessed impact includes full confidentiality, integrity, and availability loss.

Executive priority

Treat as urgent patching for browsers and mail clients, especially on managed endpoints with internet access. There is no provided evidence of active exploitation, but the critical score and sandbox-escape class justify rapid validation, update rollout, and exception tracking.

Technical view

Mozilla describes an incorrect boundary condition in the Graphics component causing a sandbox escape, mapped to CWE-119. The CVSS 3.1 score is 9.8 with network attack vector, low complexity, no privileges, and no user interaction. Mozilla says it is fixed in Firefox 147, Firefox ESR 115.32/140.7, Thunderbird 147, and Thunderbird 140.7.

Likely exposure

Likely exposure is Mozilla Firefox or Thunderbird installations that have not reached the fixed versions named by Mozilla. Red Hat references and errata indicate downstream Linux packages may also require vendor updates. The bundle does not provide a complete affected-version range beyond the fixed releases.

Exploitation context

The source bundle marks CISA KEV as false and provides no cited evidence of active exploitation. The score and vector indicate serious theoretical exploitability, but exploit availability, real-world targeting, and attack prerequisites beyond the CVSS vector are not established in the provided sources.

Researcher notes

Key gaps remain: the public bundle does not include exploit details, complete affected ranges, or proof of exploitation. Focus validation on version and package state, not exploit reproduction. Bugzilla may contain restricted details, so rely on Mozilla and vendor advisories for remediation status.

Mitigation direction

  • Update Firefox to 147 or the relevant ESR fixed release.
  • Update Thunderbird to 147 or 140.7 where applicable.
  • Apply Red Hat security errata for affected distro packages.
  • Check Mozilla and OS vendor guidance for deployment-specific remediation.
  • Prioritize managed browser and mail-client fleets before lower-risk endpoints.

Validation and detection

  • Inventory Firefox and Thunderbird versions across endpoints.
  • Confirm installed versions meet or exceed Mozilla fixed releases.
  • Check Linux package status against Red Hat advisories if applicable.
  • Review vulnerability scanner findings for CVE-2026-0879 after patching.
  • Document exceptions where fixed versions are unavailable.
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-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.

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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.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-0879 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
9.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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
33Source 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
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9CISA-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

9.8Critical
CVSS 3.1 vector shape for CVE-2026-0879Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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: Sandbox escape due to incorrect boundary conditions in the Graphics component
other:Red Hat severity ratingcvssV3_1
  • 2026-01-13T14:02:19.289Z: Reported to Red Hat.
  • 2026-01-13T13:30:54.207Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.32, 140.7, 147Listed
MozillaThunderbird140.7, 147Listed
Weakness

CWE details

CWE-119

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

CWE-119 · source CWE mapping

Improper Restriction of Operations within the Bounds of a Memory Buffer

Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs