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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

A flaw in Mozilla’s Graphics component could let an attacker escape Firefox or Thunderbird’s sandbox, weakening a key containment layer. Mozilla says it was fixed in Firefox 147, Firefox ESR 115.32/140.7, Thunderbird 147, and Thunderbird 140.7. Treat unpatched endpoints as urgent because the CVSS impact is high for confidentiality, integrity, and availability.

Executive priority

Prioritize remediation quickly across managed desktops and servers with packaged Mozilla components. There is no supplied evidence of active exploitation, but the critical rating and sandbox escape class make delayed patching a material endpoint risk.

Technical view

CVE-2026-0879 is a CWE-119 sandbox escape caused by incorrect boundary conditions in the Graphics component. The provided CVSS v3.1 score is 9.8 with AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. The bundle does not provide exploit mechanics, vulnerable version ranges, or proof-of-concept details.

Likely exposure

Exposure is most likely on endpoints running Mozilla Firefox, Firefox ESR, or Thunderbird below the fixed releases named by Mozilla. Red Hat references indicate downstream packaged products also required security updates. Exact vulnerable version ranges are not fully shown in the supplied bundle.

Exploitation context

The bundle marks KEV as false and provides no cited evidence of active exploitation. The severity comes from sandbox escape impact and the CVSS 9.8 rating, not from confirmed exploitation in the supplied sources.

Researcher notes

The public bundle identifies the component, weakness class, CVSS vector, fixed releases, and vendor advisories, but not exploit primitives or affected version ranges. Analysis should stay tied to Mozilla advisories, Bugzilla, CVE data, and downstream Red Hat errata.

Mitigation direction

  • Update Firefox to version 147 or later.
  • Update Firefox ESR to 115.32 or 140.7 or later.
  • Update Thunderbird to 147 or 140.7 or later.
  • Apply relevant Red Hat security errata for packaged Mozilla builds.
  • Check Mozilla and OS vendor guidance for any additional instructions.

Validation and detection

  • Inventory installed Firefox, Firefox ESR, and Thunderbird versions.
  • Confirm endpoints meet or exceed the fixed versions named by Mozilla.
  • Verify Red Hat systems have applicable RHSA updates installed.
  • Review vulnerability scanner results for CVE-2026-0879 closure.
  • Track exceptions where browser or mail clients cannot be updated promptly.
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-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.

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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.

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