Security readout for executives and security teams
Plain-English summary
A logged-in remote attacker could disrupt new sign-ins to Cisco Unified CM IM and Presence Service. Existing authenticated users are reported as unaffected, but the authentication service can restart and deny new login attempts. The business impact is communications availability, not data theft or system takeover.
Executive priority
Treat as moderate priority unless the service is internet-exposed or critical to daily operations. The flaw can disrupt collaboration onboarding and new sessions, but sources indicate no confidentiality or integrity impact and no confirmed active exploitation.
Technical view
CVE-2020-27121 is improper handling of login requests in Cisco Unified CM IM&P. With valid credentials, a remote attacker can trigger the Cisco XCP Authentication Service to crash or restart, causing limited availability impact for new logins. CVSS v3.1 is 4.3.
Likely exposure
Exposure is most relevant for organizations running Cisco Unified Communications Manager IM and Presence Service with reachable client login paths. The provided sources do not list specific affected versions, fixed releases, or CPEs.
Exploitation context
The bundle supports authenticated remote denial of service only. It does not show CISA KEV listing or other evidence of active exploitation. The attack requires credentials and affects new login attempts, while already authenticated users are not affected.
Researcher notes
Key uncertainty is version specificity: the source bundle lists the product but not affected or fixed versions. Research should focus on Cisco advisory details, service exposure, authentication scope, and telemetry for XCP Authentication Service instability.
Mitigation direction
- Review the Cisco advisory for affected releases, fixed software, and workaround details.
- Limit IM&P login access to trusted networks where operationally possible.
- Monitor authentication service restarts and unusual login request patterns.
- Prioritize remediation for externally reachable or business-critical collaboration environments.
Validation and detection
- Confirm whether Cisco Unified CM IM and Presence Service is deployed.
- Inventory exact IM&P software versions and compare them with Cisco guidance.
- Check whether the Cisco XCP Authentication Service has unexpected restart events.
- Verify whether any vendor-documented workaround is already implemented.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-248: Exact CWE lookup
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Open ATT&CK lookupCVE-2020-27121 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- 20201104 Cisco Unified Communications Manager IM and Presence Service Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.