CVE-2021-21621Network attack vector

User impersonation via exposed session ID

Published Feb 24, 2021 · Updated Aug 3, 2024

Information disclosure in Jenkins Support Core Plugin 2.72 and earlier allows attackers to obtain a bundle creator's session ID. The About user collector writes the creator's serialized authentication object to user.md instead of limiting output to basic identity details. Exploitation requires access to the bundle and the same Jenkins instance; configurations that serialize the session ID enable impersonation of the creator.

CVSS severity5.3
Medium
EPSS probability1.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Information disclosure in Jenkins Support Core Plugin 2.72 and earlier allows attackers to obtain a bundle creator's session ID. The About user collector writes the creator's serialized authentication object to user.md instead of limiting output to basic identity details. Exploitation requires access to the bundle and the same Jenkins instance; configurations that serialize the session ID enable impersonation of the creator.

The record

CVE
CVE-2021-21621
Published
Feb 24, 2021
Updated
Aug 3, 2024
Vendor
Jenkins Project
Product
Support Core Plugin
Classifications
CWE-200, T1550.004
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=unspecified <=2.72

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Jenkins Project · Support Core Pluginversion=unspecified <=2.72

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1550.004Use Alternate Authentication Material: Web Session Cookie

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo