Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2024-20420 is a medium-severity Execution with Unnecessary Privileges (CWE-250) vulnerability in Cisco Ata 191 Firmware. Its CVSS base score is 5.4 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data Obfuscation (T1001); ranked at the 28th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-24 (Access Control Decisions) and AC-25 (Reference Monitor) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2024-18135
Vulnerability Data
A vulnerability in the web-based management interface of Cisco ATA 190 Series Analog Telephone Adapter firmware could allow an authenticated, remote attacker with low privileges to run commands as an Admin user. This vulnerability is due to incorrect authorization verification…
more
by the HTTP server. An attacker could exploit this vulnerability by sending a malicious request to the web-based management interface. A successful exploit could allow the attacker to run commands as the Admin user.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 4 hardening rules · 4 OS baselines
V10.2.3V13.2.2
Mitigating Controls (NIST 800-53 r5) AI
AC-3 directly requires correct enforcement of authorization decisions on every access request, structurally preventing incorrect checks.
AC-24 ensures access-control decisions are made and applied consistently, reducing the chance of an incorrect authorization result.
A reference monitor that is always invoked and tamper-proof forces every authorization decision through a verified, correct path.
Least privilege directly requires that only the minimum necessary authorizations are granted, structurally eliminating execution with unnecessary privileges.
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.AA-05 directly enforces least privilege so largely eliminates CWE-250 at design time, yet the weakness can still arise from runtime escalation paths, third-party code, or misapplied role definitions outside this single control.
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.5.15's policy, requirements, and rules for determining/minimizing access rights (incl. privileged access restrictions, need-to-know, least-privilege-like mapping, and role-based consistency) directly stop most unnecessary-privilege execution by design; bounded remainder is runtime elevation or misconfigured enforcement that still requires other controls (e.g. 8.2, 8.3) to act.
Requiring explicit justification and time-limited grants discourages the routine allocation of unnecessary privileges that would otherwise allow execution with more rights than required.
Independent scrutiny can identify processes or services still running with unnecessary privileges and drive their reduction before an attacker can abuse them.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).
Windows 10 (1 rule)
- V-220712 Only accounts responsible for the administration of a system must have Administrator rights on the system. blocks CWE-250
Windows Server 2016 (1 rule)
- V-225007 Only administrators responsible for the member server or standalone or nondomain-joined system must have Administrator rights on the system. blocks CWE-250
Windows Server 2019 (1 rule)
- V-205746 Windows Server 2019 must only allow Administrators responsible for the member server or standalone or nondomain-joined system to have Administrator rights on the system. blocks CWE-250