Cisco Unified Communications Manager IM and Presence Service Denial of Service Vulnerability

published 2020-11-06 6y ago modified 2026-06-17 4mo ago also EUVD-2020-19645

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.2%; EPSS 1.2% chance of exploitation in 30 days, percentile 67%
public exploits: 0; none known

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.

Is CVE-2020-27121 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: last yr. (2024-11-13)

Exploit prediction

1.16% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
NVD	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	4.0	AV:N/AC:L/Au:S/C:N/I:N/A:P

Affected products

Cisco Cisco Unified Communications Manager IM and Presence Service

Classification

Weakness

CWE-248 Uncaught Exception
CWE-755 Improper Handling of Exceptional Conditions

References

tools.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-imp-dos-uTx2dqu2
vendor-advisory

Sources

CVE List CVE-2020-27121
NVD CVE-2020-27121

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.