CVE-2025-20255 is a medium-severity vulnerability affecting the client join services of Cisco Webex Meetings. The flaw arises from improper handling of HTTP requests within the meeting join service, specifically related to the caching mechanism of HTTP responses. An unauthenticated, remote attacker can exploit this vulnerability by crafting malicious HTTP requests that manipulate the cached HTTP responses, a technique known as HTTP cache poisoning. This manipulation causes the Webex Meetings service to return incorrect or malicious HTTP responses to clients attempting to join meetings. Although the vulnerability does not directly compromise confidentiality or availability, it impacts the integrity of the data served by the Webex Meetings client join service. The attack requires no authentication but does require user interaction, such as a user joining a meeting and receiving the manipulated response. The CVSS score of 4.3 reflects a medium severity, with no direct confidentiality or availability impact but a potential integrity impact. There are no known exploits in the wild at this time, and no patches or affected versions have been explicitly listed yet. The vulnerability was published on May 21, 2025, and was reserved in October 2024. The lack of patch information suggests that mitigation may currently rely on workarounds or monitoring until an official fix is released by Cisco.

For European organizations, this vulnerability poses a risk primarily to the integrity of Webex Meetings communications. Since Webex is widely used for corporate communications, manipulation of HTTP responses could lead to misinformation being presented to users, potentially facilitating social engineering, phishing, or session manipulation attacks. Although the vulnerability does not directly expose sensitive data or disrupt service availability, the integrity compromise could undermine trust in meeting content or lead to further exploitation by attackers leveraging manipulated meeting join responses. Organizations relying heavily on Webex for sensitive or regulated communications could face compliance risks if manipulated data leads to unauthorized actions or data leakage. The impact is heightened in sectors such as finance, government, and critical infrastructure where Webex is commonly used and where meeting integrity is crucial.

1. Monitor Cisco’s official security advisories closely for patches addressing CVE-2025-20255 and apply updates promptly once available. 2. Implement network-level protections such as Web Application Firewalls (WAFs) that can detect and block suspicious HTTP request patterns indicative of cache poisoning attempts. 3. Employ strict HTTP cache-control headers and validate caching policies within the Webex client environment if configurable, to limit the impact of cache poisoning. 4. Educate users about the risks of interacting with unexpected or suspicious meeting join links and encourage verification of meeting sources before joining. 5. Use network segmentation and zero-trust principles to limit exposure of Webex client services to untrusted networks. 6. Monitor logs and network traffic for anomalies in HTTP responses related to Webex meetings to detect potential exploitation attempts early. 7. Consider temporary mitigation by restricting or filtering HTTP caching behaviors at proxy or gateway levels until an official patch is released.