Security readout for executives and security teams
Plain-English summary
A critical memory-safety flaw affects Mozilla's JavaScript/WebAssembly component in Firefox and Thunderbird. Successful exploitation could expose data, alter application behavior, or cause crashes. Mozilla identifies patched releases, but the supplied evidence does not define the complete vulnerable version range.
Executive priority
Treat this as an urgent enterprise patching event because the potential impact is complete application compromise and the CVSS attack conditions are favorable. Expedite updates, verify coverage, and track exceptions. There is currently no supplied evidence of active exploitation.
Technical view
CVE-2026-74936 is a CWE-416 use-after-free in the JavaScript/WebAssembly component. Its CVSS 3.1 score is 9.8, reflecting network reachability, low complexity, no required privileges or user interaction, and potentially high confidentiality, integrity, and availability impact.
Likely exposure
Organizations using Firefox or Thunderbird releases older than the applicable fixed version may be exposed. Fixes are Firefox 154, ESR 140.14, ESR 153.1, Thunderbird 154, 140.14, and 153.1. Exact vulnerable lower bounds are not supplied.
Exploitation context
The CVE is not listed as KEV, and the supplied sources do not confirm active exploitation or a public exploit. The CVSS vector indicates a network-reachable, low-complexity condition requiring neither privileges nor user interaction, but practical trigger conditions and exploit reliability remain undisclosed.
Researcher notes
The public bundle provides the component, weakness class, CVSS vector, and fixed releases, but no root-cause detail, vulnerable version lower bounds, trigger mechanics, proof of concept, or exploitation telemetry. The listed release numbers should be interpreted as fixed versions based on Mozilla's description, not vulnerable versions.
Mitigation direction
- Update Firefox to 154, ESR 140.14, ESR 153.1, or a later applicable release.
- Update Thunderbird to 154, 140.14, 153.1, or a later applicable release.
- Prioritize internet-facing and broadly deployed endpoints for accelerated patching.
- Consult Mozilla advisories for platform-specific packages and any revised guidance.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across managed endpoints.
- Verify every installation meets or exceeds its applicable fixed release.
- Confirm deployment tooling reports successful installation and application restart where required.
- Monitor Mozilla advisories and Bugzilla for revised affected ranges or exploitation information.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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-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.
Open ATT&CK lookupCVE-2026-74936 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- 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
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.
SSVC decision data
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2052688CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-74/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-76/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-77/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-78/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-79/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-80/CVE reference, mozilla
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.