Security readout for executives and security teams
Plain-English summary
CVE-2021-29955 is a Mozilla Firefox transient execution issue named Floating Point Value Injection. In affected versions, it could leak arbitrary memory addresses and may have contributed to JIT type confusion. Business impact is mainly for endpoints still running old Firefox or Firefox ESR builds.
Executive priority
Treat as a hygiene-driven browser update issue unless legacy Firefox remains in use. Prioritize verification in endpoint management because browser memory issues can affect user workstations, but no active exploitation is shown in the provided sources.
Technical view
The issue affects Firefox ESR before 78.9 and Firefox before 87. Mozilla states FPVI could leak arbitrary memory addresses and may have enabled JIT type confusion. The related SCSB issue did not affect Firefox. The provided sources do not include CVSS, CWE, exploit details, or active exploitation evidence.
Likely exposure
Exposure is likely limited to systems using Firefox ESR below 78.9 or Firefox below 87. Current managed browser fleets should confirm versions rather than assume coverage.
Exploitation context
The source bundle does not show CISA KEV listing or any cited active exploitation. Public details describe potential memory disclosure and possible JIT type confusion, but do not provide confirmed exploitation status.
Researcher notes
Evidence is limited to Mozilla/CVE descriptions. The key technical claim is FPVI-related transient execution causing arbitrary memory address leakage, with possible JIT type confusion. Avoid assuming SCSB impact because Mozilla states that related issue did not affect Firefox.
Mitigation direction
- Upgrade Firefox to version 87 or later.
- Upgrade Firefox ESR to version 78.9 or later.
- Check Mozilla advisory guidance for any environment-specific recommendations.
- Remove unsupported browser versions from managed endpoint baselines.
Validation and detection
- Inventory installed Firefox and Firefox ESR versions across endpoints.
- Flag Firefox below 87 and Firefox ESR below 78.9.
- Confirm browser update controls prevent downgrade or unmanaged legacy installs.
- Review vulnerability scanner findings against Mozilla advisory version thresholds.
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
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CVE-2021-29955 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.mozilla.org/security/advisories/mfsa2021-10/CVE reference · x_refsource_MISC
- https://www.mozilla.org/security/advisories/mfsa2021-11/CVE reference · x_refsource_MISC
- https://bugzilla.mozilla.org/show_bug.cgi?id=1692972CVE reference · x_refsource_MISC
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.