CVE-2021-29842Network attack vector

Username enumeration via differential login responses

Published Sep 16, 2021 · Updated Sep 17, 2024

Username enumeration in IBM WebSphere Application Server and Liberty allows remote attackers to identify valid accounts through login attempts. Federated-repository authentication returns observably different responses for valid and invalid usernames. Exposure requires a federated repository, and unauthenticated network access is enough to disclose which submitted usernames correspond to accounts.

CVSS severity3.7
Low
EPSS probability1.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Username enumeration in IBM WebSphere Application Server and Liberty allows remote attackers to identify valid accounts through login attempts. Federated-repository authentication returns observably different responses for valid and invalid usernames. Exposure requires a federated repository, and unauthenticated network access is enough to disclose which submitted usernames correspond to accounts.

The record

CVE
CVE-2021-29842
Published
Sep 16, 2021
Updated
Sep 17, 2024
Vendor
IBM
Product
IBM WebSphere Application Server
Classifications
CWE-307, CAPEC-565, CAPEC-49, CAPEC-600, CAPEC-652, CAPEC-653, CAPEC-560, CAPEC-16, T1589.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record 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=7.0
  2. Affected versionversion=8.0
  3. Affected versionversion=8.5
  4. Affected versionversion=9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

IBM · IBM WebSphere Application Serverversion=7.0; version=8.0; version=8.5; version=9.0
IBM · IBM WebSphere Application Server Libertyversion=17.0.0.3; version=21.0.0.9

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
3.7IBM CorporationCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
5.3NIST NVDCVSS: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-307Improper Restriction of Excessive Authentication Attempts
CAPEC-565Password Spraying
CAPEC-49Password Brute Forcing
CAPEC-600Credential Stuffing
CAPEC-652Use of Known Kerberos Credentials
CAPEC-653Use of Known Operating System Credentials
CAPEC-560Use of Known Domain Credentials
CAPEC-16Dictionary-based Password Attack
T1589.003Gather Victim Identity Information: Employee Names

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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