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CVE Record

CVE-2026-74940: Use-after-free in the Graphics: Text component

Use-after-free in the Graphics: Text component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

Mozilla fixed a use-after-free flaw in Firefox and Thunderbird’s Graphics: Text component. The critical 9.8 rating indicates that successful exploitation could seriously affect confidentiality, integrity, and availability. Organizations should rapidly identify installations older than the listed fixed releases and update them.

Executive priority

Treat this as an urgent patching priority because widely deployed client applications are involved and the supplied severity is critical. Accelerate updates, measure remaining outdated installations, and escalate exceptions. Active exploitation is not established by the provided evidence.

Technical view

CVE-2026-74940 is a CWE-416 use-after-free in Mozilla’s Graphics: Text component. The supplied CVSS 3.1 vector rates it network-accessible, low-complexity, requiring neither privileges nor user interaction, with high confidentiality, integrity, and availability impacts. The sources do not provide detailed trigger conditions or affected-version boundaries.

Likely exposure

Exposure is likely wherever Firefox or Thunderbird remains below the applicable fixed release: Firefox 154, ESR 115.39, ESR 140.14, ESR 153.1; Thunderbird 154, 140.14, or 153.1. The bundle does not identify affected operating systems or exact vulnerable starting versions.

Exploitation context

The supplied record is not listed in KEV, and no provided source states that active exploitation has occurred. The critical CVSS characteristics indicate substantial theoretical risk, but they do not prove exploit availability or real-world attacks. No indicators of compromise are provided.

Researcher notes

The public description identifies the component and memory-lifetime weakness but omits trigger conditions, root-cause detail, exploitability analysis, and indicators. The listed versions are described as fixed releases, despite appearing under the bundle’s affected field. Researchers should avoid interpreting those fixed versions as vulnerable without additional vendor clarification.

Mitigation direction

  • Update Firefox to 154 or the applicable fixed ESR release.
  • Update Thunderbird to 154, 140.14, or 153.1, as applicable.
  • Restart updated applications to ensure fixed binaries are active.
  • Temporarily restrict outdated installations when immediate updating is impossible.
  • Monitor Mozilla advisories for revised affected-version or mitigation information.

Validation and detection

  • Inventory Firefox and Thunderbird versions across managed and unmanaged endpoints.
  • Compare each installation with the fixed release for its specific update channel.
  • Verify applications restarted and report the expected fixed version.
  • Confirm endpoint management shows successful update deployment without persistent failures.
  • Document exceptions and verify Mozilla guidance before declaring unsupported branches safe.
Prepared
Confidence
medium
Sources
9

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-416: 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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cve · low confidence lookup

CVE-2026-74940 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.

1CVSS vectors
3Timeline events
1ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

1 official score

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

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2026-74940Attack 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. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MozillaFirefox115.39, 140.14, 153.1, 154Listed
MozillaThunderbird140.14, 153.1, 154Listed
Weakness

CWE details

CWE-416

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

CWE-416 · source CWE mapping

Use After Free

Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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