VulnerabilityPublished 24 Sep 2025Updated 26 Sep 2025

CVE-2025-20240: Cisco IOS XE Software · Incomplete Blacklist to Cross-Site Scripting

Affects Cisco IOS XE SoftwareSource CVE Database V5

Not known to be exploited · CVSS 6.1 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

6.1Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 26% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Cisco Cisco IOS XE Software	Affected 16.6.1 – 17.16.1 91 affected builds	Fixed in–

AI-suggested

To mitigate this vulnerability effectively, European organizations should take the following specific actions: 1) Immediately identify all Cisco IOS XE devices running affected versions (16.6.1 through 17.16.1a) by conducting an inventory and version audit. 2) Apply Cisco-released patches or updates that address CVE-2025-20240 as soon as they become available; if patches are not yet released, monitor Cisco advisories closely. 3) Restrict access to the web authentication interface by implementing network segmentation and firewall rules to limit management interface exposure only to trusted internal networks or VPNs. 4) Employ web application firewalls (WAFs) or intrusion prevention systems (IPS) capable of detecting and blocking reflected XSS attack patterns targeting Cisco device management portals. 5) Educate users and administrators about the risks of clicking unsolicited links, especially those purporting to be related to network device management, to reduce the likelihood of successful phishing attempts. 6) Enable multi-factor authentication (MFA) for device management interfaces to reduce the impact of stolen session cookies. 7) Regularly monitor device logs and network traffic for unusual activity indicative of attempted or successful exploitation. 8) Consider disabling the web authentication feature if it is not essential or replacing it with more secure authentication mechanisms. These targeted measures go beyond generic advice by focusing on reducing attack surface, enforcing strict access controls, and enhancing user awareness specific to this vulnerability.

Description

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. 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.

Impact

For European organizations, this vulnerability poses a significant risk to network security and user privacy. Cisco IOS XE devices are widely deployed in enterprise and service provider networks across Europe, often serving as routers, switches, and access control points. Exploitation of this XSS vulnerability could allow attackers to hijack administrative sessions or user credentials, potentially leading to unauthorized configuration changes, data interception, or lateral movement within the network. Given the critical role of Cisco IOS XE devices in managing network traffic and security policies, a successful attack could undermine network integrity and confidentiality. Additionally, the theft of session cookies could facilitate further attacks, including privilege escalation or persistent access. The requirement for user interaction means that phishing or social engineering campaigns could be used to lure users into clicking malicious links, increasing the attack surface. European organizations with remote or web-based management interfaces exposed to untrusted networks are particularly vulnerable. The impact is heightened in sectors with stringent data protection regulations such as GDPR, where unauthorized data access or breaches could result in severe legal and financial consequences. Moreover, the reflected XSS could be used as a stepping stone for more sophisticated attacks targeting critical infrastructure or sensitive data within European enterprises.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-webui-xss-VWyDgjOU (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 2 Oct 2025, 00:35 UTC

Technical details

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