CVE-2020-27121: A vulnerability in Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P) Software could allow an authenticated, remote ...

Description

A vulnerability in Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P) Software could allow an authenticated, remote attacker to cause the Cisco XCP Authentication Service on an affected device to restart, resulting in a denial of service (DoS) condition. The vulnerability is due to improper handling of login requests. An attacker could exploit this vulnerability by sending a crafted client login request to an affected device. A successful exploit could allow the attacker to cause a process to crash, resulting in a DoS condition for new login attempts. Users who are authenticated at the time of the attack would not be affected. There are workarounds that address this vulnerability.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.15%

62.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Cisco	Unified Communications Manager Im And Presence Service	12.5\(1\)

References

Timeline

Published: Nov 6, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-27121?

A vulnerability in Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P) Software could allow an authenticated, remote attacker to cause the Cisco XCP Authentication Service on an affected device to restart, resulting in a denial of service (DoS) condition. The vulnerability is due to improper handling of login requests. An attacker could exploit this vulnerability by sending a crafted client login request to an affected device. A successful exploit could allow the attacker to cause a process to crash, resulting in a DoS condition for new login attempts. Users who are authenticated at the time of the attack would not be affected. There are workarounds that address this vulnerability.

How severe is CVE-2020-27121?

CVE-2020-27121 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.15% probability of exploitation in the next 30 days.

How do I fix CVE-2020-27121?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.