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CVE Record

CVE-2026-4685: Incorrect boundary conditions in the Graphics: Canvas2D component

Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-4685 is a high-severity Mozilla graphics bug in Canvas2D. The sourced impact is availability: vulnerable Firefox or Thunderbird builds may crash or become unavailable when processing malicious content. Mozilla fixed it in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Executive priority

Treat this as a high-priority endpoint patching issue, not a confirmed active-exploitation emergency. The business risk is disruption from browser or mail-client instability, with broad exposure wherever Mozilla clients are deployed.

Technical view

The issue is incorrect boundary handling in Graphics: Canvas2D, mapped to CWE-754 and CWE-787. CVSS 3.1 is 7.5: network reachable, low complexity, no privileges, no user interaction, unchanged scope, and high availability impact only. Sources do not substantiate confidentiality, integrity, or code-execution impact.

Likely exposure

Organizations are most exposed on endpoints using Firefox, Firefox ESR, or Thunderbird versions older than the fixed Mozilla releases. Red Hat-packaged Mozilla components may also require vendor errata review. Server exposure is likely indirect unless Mozilla components are used in automation or rendering workflows.

Exploitation context

The source bundle says KEV is false, and no provided source confirms active exploitation. The CVSS vector indicates remote, unauthenticated, low-complexity availability impact without user interaction, but the public details provided are not enough to describe a proven exploit chain.

Researcher notes

Public details identify Canvas2D boundary handling and CWE-787, but do not provide root-cause depth or a confirmed exploit path. Avoid assuming code execution because the supplied CVSS impact is availability-only. Validate against vendor advisories and package metadata.

Mitigation direction

  • Update Firefox to 149, ESR 115.34, ESR 140.9, or later supported releases.
  • Update Thunderbird to 149, 140.9, or later supported releases.
  • Apply relevant Red Hat security advisories for packaged Mozilla components.
  • Prioritize managed endpoint browser and mail-client patch compliance.
  • Check Mozilla and distribution guidance for any environment-specific mitigations.

Validation and detection

  • Inventory Firefox, Firefox ESR, and Thunderbird versions across endpoints.
  • Confirm installed versions meet or exceed the fixed releases.
  • Check Red Hat systems for applicable RHSA errata installation.
  • Review vulnerability scanner results for CVE-2026-4685 after patching.
  • Track exceptions where legacy ESR versions cannot be upgraded promptly.
Prepared
Confidence
high
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-754: 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-787: 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
cve · low confidence lookup

CVE-2026-4685 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
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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: partial

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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADP
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-4685Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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: Incorrect boundary conditions in the Graphics: Canvas2D component
other:Red Hat severity ratingcvssV3_1
  • 2026-03-24T13:02:07.309Z: Reported to Red Hat.
  • 2026-03-24T12:30:21.064Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.34, 140.9, 149Listed
MozillaThunderbird140.9, 149Listed
Weakness

CWE details

CWE-754CWE-787

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

CWE-754 · source CWE mapping

Improper Check for Unusual or Exceptional Conditions

Improper Check for Unusual or Exceptional Conditions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-787 · source CWE mapping

Out-of-bounds Write

Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs