Security readout for executives and security teams
Plain-English summary
A critical flaw was reported in Firefox Focus for Android and fixed in Firefox 155. The supplied CVSS assessment indicates possible remote compromise without authentication or user interaction, with serious confidentiality, integrity, and availability impact. Public details are limited, so the practical attack mechanism remains unclear.
Executive priority
Treat this as an urgent mobile-browser update, especially where Firefox Focus accesses sensitive accounts or organizational data. Prioritize rapid inventory and remediation, while recognizing that public technical evidence is sparse and active exploitation is not established.
Technical view
CVE-2026-84135 is classified as CWE-200 and scored CVSS 3.1 9.8: network-accessible, low complexity, no privileges, and no user interaction. Mozilla states the issue was fixed in Firefox 155. The bundle does not explain the root cause or reconcile the CWE information-exposure classification with the full confidentiality, integrity, and availability impact ratings.
Likely exposure
Firefox Focus for Android installations lacking the Firefox 155 fix are the likely concern. The supplied affected-version entry lists Firefox 155 despite stating the vulnerability was fixed in 155, creating version ambiguity. Confirm Firefox Focus package versions and Mozilla’s applicability guidance before declaring systems vulnerable or safe.
Exploitation context
The CVSS vector describes an unauthenticated, network-reachable attack requiring no user interaction. However, the supplied sources provide no attack-path details, proof of concept, or evidence of exploitation in the wild. The CVE is not listed as KEV in the bundle.
Researcher notes
The record supplies a critical CVSS vector but only an “Other issue” description. CWE-200 suggests information exposure, while the vector claims complete confidentiality, integrity, and availability impact. The affected entry and fixed-version statement also conflict. Researchers should avoid inferring root cause, exploitability mechanics, or exact vulnerable versions without further Mozilla disclosure.
Mitigation direction
- Update Firefox Focus for Android to a release containing the Firefox 155 fix.
- Use managed application controls to accelerate updates across organizational Android devices.
- Check Mozilla’s advisory for clarified affected versions and any additional mitigation guidance.
- Restrict use of outdated installations until their remediation status is confirmed.
Validation and detection
- Inventory Firefox Focus installations and record their exact Android application versions.
- Verify installed builds contain the fix identified with Firefox 155.
- Review Mozilla’s advisory and Bugzilla record for updated applicability details.
- Re-scan managed devices after deployment and investigate any remaining outdated installations.
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-200: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. 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-2026-84135 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=2046661CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-82/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.
Exposure of Sensitive Information to an Unauthorized Actor
Exposure of Sensitive Information to an Unauthorized Actor represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.