CVE-2026-20195Network attack vector

User account enumeration via differentiated API errors

Published May 6, 2026 · Updated May 6, 2026

Observable response discrepancy in Cisco Identity Services Engine allows remote attackers to enumerate valid user accounts through its API. The identity management endpoint returns differentiated error messages for crafted requests, exposing whether each submitted username exists. No authentication or special device configuration is required, and the disclosed consequence is limited to compiling valid usernames.

CVSS severity5.3
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Observable response discrepancy in Cisco Identity Services Engine allows remote attackers to enumerate valid user accounts through its API. The identity management endpoint returns differentiated error messages for crafted requests, exposing whether each submitted username exists. No authentication or special device configuration is required, and the disclosed consequence is limited to compiling valid usernames.

The record

CVE
CVE-2026-20195
Published
May 6, 2026
Updated
May 6, 2026
Vendor
ClamAV
Product
Cisco Identity Services Engine
Classifications
CWE-204, T1087
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 6, 2026CVE publishedPublication date reported by the CVE source.
  2. May 6, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.3.0
  2. Affected versionversion=3.3 Patch 1
  3. Affected versionversion=3.3 Patch 10
  4. Affected versionversion=3.3 Patch 2
  5. Affected versionversion=3.3 Patch 3
  6. Affected versionversion=3.3 Patch 4
  7. Affected versionversion=3.3 Patch 5
  8. Affected versionversion=3.3 Patch 6
  9. Affected versionversion=3.3 Patch 7
  10. Affected versionversion=3.3 Patch 8
  11. Affected versionversion=3.3 Patch 9
  12. Affected versionversion=3.4.0
  13. Affected versionversion=3.4 Patch 1
  14. Affected versionversion=3.4 Patch 2
  15. Affected versionversion=3.4 Patch 3
  16. Affected versionversion=3.4 Patch 4
  17. Affected versionversion=3.4 Patch 5
  18. Affected versionversion=3.5.0
  19. Affected versionversion=3.5 Patch 1
  20. Affected versionversion=3.5 Patch 2
  21. Affected versionversion=3.5 Patch 3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Identity Services Engineversion=3.3.0; version=3.3 Patch 1; version=3.3 Patch 10; version=3.3 Patch 2; version=3.3 Patch 3; version=3.3 Patch 4; version=3.3 Patch 5; version=3.3 Patch 6; version=3.3 Patch 7; version=3.3 Patch 8; version=3.3 Patch 9; version=3.4.0; version=3.4 Patch 1; version=3.4 Patch 2; version=3.4 Patch 3; version=3.4 Patch 4; version=3.4 Patch 5; version=3.5.0; version=3.5 Patch 1; version=3.5 Patch 2; version=3.5 Patch 3

Published CVSS scores

5.3Cisco PSIRTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-204Observable Response Discrepancy
T1087Account Discovery

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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