Security readout for executives and security teams
Plain-English summary
A flaw in Mozilla’s Cache API could bypass an intended security protection, allowing a remote attacker to compromise sensitive information and alter data without credentials or user interaction. The supplied record rates it critical, but does not describe the underlying attack technique.
Executive priority
Treat remediation as urgent because exploitation is rated remotely reachable, low complexity, and capable of high confidentiality and integrity impact. Expedite supported Mozilla updates, while avoiding claims of ongoing attacks because none are established in the supplied evidence.
Technical view
CVE-2026-74959 is a CWE-693 protection-mechanism failure in the Storage: Cache API component. Its CVSS 3.1 score is 9.1, with network reachability, low complexity, no privileges, and no user interaction; confidentiality and integrity impacts are high, while availability impact is none.
Likely exposure
Firefox and Thunderbird installations on affected release tracks that have not reached the specified fixed versions are the likely exposure. The bundle does not provide exact vulnerable version ranges, so inventory comparisons should use Mozilla’s individual product advisories.
Exploitation context
The CVSS vector indicates potentially remote, unauthenticated exploitation without user interaction. However, the supplied sources provide no exploit mechanics, observed attacks, or proof-of-concept status. The CVE is not listed as KEV in the bundle, so active exploitation is not established.
Researcher notes
Public details in the bundle are limited to a mitigation bypass in Storage: Cache API, CWE-693, the CVSS vector, and fixed releases. Product-specific advisories should be used to establish exact affected ranges. The evidence does not support conclusions about exploit primitives, sandbox impact, affected operating systems, or attack prevalence.
Mitigation direction
- Update Firefox to 154, ESR 140.14, ESR 153.1, or a later supported release.
- Update Thunderbird to 154, 140.14, 153.1, or a later supported release.
- Use the applicable Mozilla advisory to confirm the correct release track.
- Prioritize unmanaged browsers and email clients that may not receive automatic updates.
Validation and detection
- Inventory deployed Firefox and Thunderbird versions across endpoints.
- Confirm each installation meets its release track’s fixed version.
- Verify update-management reports against endpoint-level version evidence.
- Review Mozilla’s applicable advisory for product-specific affected-version details.
Public sources used
- CVE Program record for CVE-2026-74959
- CVE List V5 record
- Mozilla Bug 2047853
- Mozilla Security Advisory MFSA 2026-74
- Mozilla Security Advisory MFSA 2026-76
- Mozilla Security Advisory MFSA 2026-77
- Mozilla Security Advisory MFSA 2026-78
- Mozilla Security Advisory MFSA 2026-79
- Mozilla Security Advisory MFSA 2026-80
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-693: 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-2026-74959 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
- 9.1 (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:N
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:N3.95.2CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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=2047853CVE 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.
Protection Mechanism Failure
Protection Mechanism Failure represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.