CVE-2023-20243
Cisco Identity Services Engine 3.1 … 3.2
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2023-20243 is a high-severity Improper Handling of Exceptional Conditions (CWE-755) vulnerability in Cisco Identity Services Engine. Its CVSS base score is 8.6 (High).
Operationally, ranked in the top 41% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-24422
Vulnerability Data
A vulnerability in the RADIUS message processing feature of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause the affected system to stop processing RADIUS packets. This vulnerability is due to improper handling of certain RADIUS…
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accounting requests. An attacker could exploit this vulnerability by sending a crafted authentication request to a network access device (NAD) that uses Cisco ISE for authentication, authorization, and accounting (AAA). This would eventually result in the NAD sending a RADIUS accounting request packet to Cisco ISE. An attacker could also exploit this vulnerability by sending a crafted RADIUS accounting request packet to Cisco ISE directly if the RADIUS shared secret is known. A successful exploit could allow the attacker to cause the RADIUS process to unexpectedly restart, resulting in authentication or authorization timeouts and denying legitimate users access to the network or service. Clients already authenticated to the network would not be affected. Note: To recover the ability to process RADIUS packets, a manual restart of the affected Policy Service Node (PSN) may be required. For more information, see the Details ["#details"] section of this advisory.
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
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.
Provides defined handling (alert and additional actions) for the exceptional condition of audit logging failure.
Supplies a concrete handling action (safe mode) for exceptional conditions, mitigating risks from improper or absent handling that could allow continued attacks.
By preparing users for contingency scenarios, the control promotes proper handling of exceptional conditions instead of default or unsafe behaviors.
An updated contingency plan defines current actions for exceptional conditions, reducing the window for attackers to exploit improper handling leading to system failure.
Procedures ensure proper handling of exceptional conditions to support effective incident response.
Incident response testing confirms proper handling of exceptional conditions to limit exploit impact.
Gives users guidance on incident handling, reducing improper handling of exceptional conditions that could stem from exploited weaknesses.
Enforces structured response to exceptional conditions so the system cannot remain in an unsafe state.
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.
Documented operating procedures may specify exception handling but do not guarantee implementation.
Logging captures unhandled exceptions, aiding detection but not preventing the weakness.
Monitoring can surface unhandled exceptions but does not enforce proper handling.
Secure SDLC mandates exception-handling requirements and testing that directly prevent improper handling of exceptional conditions.
A.8.26 explicitly lists resilience against malicious attacks including SQL injections, input validation, error message handling, and several integrity/authorization requirements that address exceptional conditions in a minority of cases, but most CWE-755 instances (e.g. unhandled nulls, resource errors, unexpected states) fall outside its named topics.
A.8.27 mandates security-by-design principles (fail securely, least privilege, defense-in-depth, distrust external input, assume-breach) plus design reviews that can catch and stop many but not all mishandlings of exceptional conditions before they reach production code; a bounded remainder (e.g. subtle runtime error paths, library-level faults, or post-review regressions) can still be present and exploitable.
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.