Cyber Resilience

CVE-2023-6135

Mozilla Firefox ≤ 121.0

Published
19 December 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 4.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
EPSS Score 0.0071 50th percentile
Risk Priority 38 floored blend · peak EPSS

Summary

CVE-2023-6135 is a medium-severity Observable Discrepancy (CWE-203) vulnerability in Mozilla Firefox. Its CVSS base score is 4.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Account Discovery (T1087); ranked in the top 50% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

Multiple NSS NIST curves were susceptible to a side-channel attack known as "Minerva". This attack could potentially allow an attacker to recover the private key. This vulnerability affects Firefox < 121.

CWE(s)
CWE-203

Related Threats

MITRE ATT&CK Enterprise Techniques

T1087 Account Discovery Discovery
Adversaries may attempt to get a listing of valid accounts, usernames, or email addresses on a system or within a compromised environment.
attack.mitre.org →
T1110 Brute Force Credential Access
Adversaries may use brute force techniques to gain access to accounts when passwords are unknown or when password hashes are obtained.
attack.mitre.org →
T1595 Active Scanning Reconnaissance
Adversaries may execute active reconnaissance scans to gather information that can be used during targeting.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-5722Same product: Mozilla Firefox
CVE-2024-5697Same product: Mozilla Firefox
CVE-2023-25741Same product: Mozilla Firefox
CVE-2024-10463Same product: Mozilla Firefox
CVE-2024-9398Same product: Mozilla Firefox
CVE-2023-25728Same product: Mozilla Firefox
CVE-2023-23597Same product: Mozilla Firefox
CVE-2025-55030Same product: Mozilla Firefox
CVE-2026-16405Same product: Mozilla Firefox
CVE-2025-6425Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 121.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 1 hardening rule · 1 OS baseline
Validate
Prove the fix (OWASP ASVS)

—

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SC-30 Concealment and Misdirection
addresses: CWE-203

Misdirection can normalize or falsify responses to eliminate observable discrepancies that aid reconnaissance.

SC-31 Covert Channel Analysis
addresses: CWE-203

Observable discrepancies in system behavior can be modulated to create covert storage or timing channels; the required analysis detects and constrains such avenues.

SI-11 Error Handling
addresses: CWE-203

Prevents attackers from using observable differences in error responses to infer internal system details or state.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly prevent observable response discrepancies via consistent error handling and timing.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.17 Clock synchronization none match
none

Accurate, synchronized timestamps reduce observable timing discrepancies that an attacker could exploit to infer sensitive information or distinguish between success and failure paths.

References