Security readout for executives and security teams
Plain-English summary
A critical flaw can bypass a security mitigation in Mozilla’s Add-ons Manager. Its CVSS assessment indicates remote exploitation without credentials or user interaction, with potentially severe confidentiality, integrity, and availability consequences. The supplied sources do not explain the bypass mechanics or confirm attacks in the wild.
Executive priority
Treat remediation as urgent because the vendor rates the issue critical and the CVSS score is 9.8. Prioritize rapid version inventory and updates across managed endpoints. Do not characterize this as an active incident without separate evidence of exploitation.
Technical view
CVE-2026-74979 is categorized as CWE-284 and scored CVSS 3.1 9.8 (network-accessible, low complexity, no privileges, no user interaction). Mozilla reports fixes in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1. The exact vulnerable version range is unclear from the bundle.
Likely exposure
Organizations using Firefox, Firefox ESR, or Thunderbird releases preceding the stated fixed versions may be exposed. The bundle’s affected-version data conflicts with its fixed-version description, so determine exposure from installed versions and Mozilla’s product-specific advisories rather than the structured affected list alone.
Exploitation context
The CVSS vector describes a remotely reachable, low-complexity condition requiring neither privileges nor user interaction. However, the bundle provides no exploit details, proof of concept, or evidence of active exploitation. The CVE is not identified as included in KEV.
Researcher notes
Publicly supplied detail is limited to a mitigation bypass in Add-ons Manager. The structured affected field lists 153.1 and 154, while the narrative identifies those numbers as fixed releases and distinguishes ESR channels. Avoid inferring root cause, affected ranges, prerequisites, or exploitability beyond the supplied CVSS vector and advisories.
Mitigation direction
- Upgrade Firefox to 154 or a later vendor-supported release.
- Upgrade Firefox ESR to 153.1 or a later vendor-supported release.
- Upgrade Thunderbird to 154, or its 153.1 supported release channel.
- Consult the applicable Mozilla advisory for product-specific guidance and deployment details.
Validation and detection
- Inventory Firefox, Firefox ESR, and Thunderbird versions across managed endpoints.
- Confirm each installation meets or exceeds its stated fixed release.
- Verify update controls successfully deployed the corrected builds.
- Review Mozilla advisories for clarified affected ranges or additional instructions.
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-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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-2026-74979 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=2045676CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-74/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/mfsa2026-80/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.
Improper Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.