Improper handling of REST API XML deserialization errors in Jenkins

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.0 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

EPSS

• CVE-2021-21604: 1.70% estimated exploitation activity in the next 30 days; percentile 77.20 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Jenkins provides XML REST APIs to configure views, jobs, and other items. When deserialization fails because of invalid data, Jenkins 2.274 and earlier, LTS 2.263.1 and earlier stores invalid object references created through these endpoints in the Old Data Monitor. If an administrator discards the old data, some erroneous data submitted to these endpoints may be persisted. This allows attackers with View/Create, Job/Create, Agent/Create, or their respective /Configure permissions to inject crafted content into Old Data Monitor that results in the instantiation of potentially unsafe objects when discarded by an administrator.\n\nJenkins 2.275, LTS 2.263.2 does not record submissions from users in Old Data Monitor anymore. In case of problems, the Java system properties hudson.util.RobustReflectionConverter.recordFailuresForAdmins and hudson.util.RobustReflectionConverter.recordFailuresForAllAuthentications can be set to true to record configuration data submissions from…

Published by the source

24 May 2022, 17:39 UTC

Last modified by the source

14 Dec 2023, 19:24 UTC

Source last checked

26 Oct 2026, 16:21 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-qv6f-rcv6-6q3x

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# Patch Next advisory brief: CVE-2021-21604

Advisory: Improper handling of REST API XML deserialization errors in Jenkins
IDs: CVE-2021-21604, GHSA-qv6f-rcv6-6q3x
Record: https://patchnext.com/advisories/cve-2021-21604 (revision 1, source checked 26 Oct 2026, 16:21 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.jenkins-ci.main:jenkins-core 2.275, 2.263.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.jenkins-ci.main:jenkins-core: affected <= 2.263.1; >= 2.264, <= 2.274; fixed in 2.275, 2.263.2

## Suggested inspection (read-only)
- Maven org.jenkins-ci.main:jenkins-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.jenkins-ci.main:jenkins-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-qv6f-rcv6-6q3x (GitHub-reviewed advisory GHSA-qv6f-rcv6-6q3x lists affected ranges: Maven org.jenkins-ci.main:jenkins-core >=0 =2.264 <=2.274)

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