Cyber Resilience

CVE-2025-20240

Published
24 September 2025
Modified
15 April 2026
CVSS Score v3.1 6.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.0027 19th percentile
Risk Priority 45 floored blend · peak EPSS

Summary

CVE-2025-20240 is a medium-severity Incomplete Denylist to Cross-Site Scripting (CWE-692) vulnerability in Cisco IOS XE (inferred from references). Its CVSS base score is 6.1 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Content Injection (T1659); ranked at the 19th 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 SI-10 (Information Input Validation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

A vulnerability in the Web Authentication feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct a reflected cross-site scripting attack (XSS) on an affected device. This vulnerability is due to improper sanitization of user-supplied input.…

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An attacker could exploit this vulnerability by persuading a user to click a malicious link. A successful exploit could allow the attacker to execute a reflected XSS attack and steal user cookies from the affected device.

CWE(s)
CWE-692

Related Threats

MITRE ATT&CK Enterprise Techniques

T1659 Content Injection Initial Access
Adversaries may gain access and continuously communicate with victims by injecting malicious content into systems through online network traffic.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-42214Shared CWE-692
CVE-2025-49590Shared CWE-692
CVE-2026-15295Shared CWE-692
CVE-2024-23569Shared CWE-692
CVE-2024-30924Shared CWE-692
CVE-2024-52305Shared CWE-692
CVE-2025-53904Shared CWE-692
CVE-2023-26047Shared CWE-692

Affected Assets

Cisco
IOS XE
inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

Input validation requires complete, allowlist-style checks that structurally eliminate reliance on incomplete XSS denylists.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles mandate robust sanitization and validation approaches that avoid incomplete denylist patterns.

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 require robust input validation and sanitization (e.g., allowlists) rather than incomplete denylists for XSS.

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.8.29 Security testing in development and acceptance mostly match
finds

Security testing can discover incomplete denylists, yet the control does not mandate their replacement.

A.8.25 Secure development life cycle partial match
prevents

Secure-SDLC processes encourage proper input/output handling, but do not specifically address denylist shortcomings.

A.8.26 Application security requirements partial match
prevents

Application-security requirements can mandate proper output encoding, but the control itself does not prescribe the technique.

A.8.28 Secure coding partial match
prevents

Secure-coding rules directly require allow-list or context-aware escaping instead of incomplete denylists for XSS.

References