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Jenkins Security Advisory 2021-05-25

This advisory announces vulnerabilities in the following Jenkins deliverables:

Descriptions

XXE vulnerability in Filesystem Trigger Plugin

SECURITY-2339 / CVE-2021-21657
Severity (CVSS): High
Affected plugin: fstrigger
Description:

Filesystem Trigger Plugin 0.40 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.

This allows attackers with Job/Configure permission or otherwise able to control the contents of an XML file being polled for changes to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the polling Jenkins controller or agent, server-side request forgery, or denial-of-service attacks.

Filesystem Trigger Plugin 0.41 disables external entity resolution for its XML parser.

XXE vulnerability in Nuget Plugin

SECURITY-2340 / CVE-2021-21658
Severity (CVSS): Medium
Affected plugin: nuget
Description:

Nuget Plugin 1.0 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks. This XML parser is used for the "Build on NuGet updates" feature.

This allows attackers with the ability to control the contents of the packages.config file in a workspace to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the Jenkins controller or server-side request forgery.

Nuget Plugin 1.1 disables external entity resolution for its XML parser.

XXE vulnerability in URLTrigger Plugin

SECURITY-2341 / CVE-2021-21659
Severity (CVSS): High
Affected plugin: urltrigger
Description:

URLTrigger Plugin 0.48 and earlier does not configure its XML parser to prevent XML external entity (XXE) attacks.

This allows attackers with Job/Configure permission or otherwise able to control the contents of an URL to an XML document being examined for changes to have Jenkins parse a crafted XML document that uses external entities for extraction of secrets from the polling Jenkins controller or agent, server-side request forgery, or denial-of-service attacks.

URLTrigger Plugin 0.49 disables external entity resolution for its XML parser.

XSS vulnerability in Markdown Formatter Plugin

SECURITY-2198 / CVE-2021-21660
Severity (CVSS): High
Affected plugin: markdown-formatter
Description:

Markdown Formatter Plugin 0.1.0 and earlier uses a Markdown library to parse Markdown that does not escape crafted link target URLs.

This results in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with the ability to edit any description rendered using the configured markup formatter.

Markdown Formatter Plugin 0.2.0 uses a different Markdown library that is not affected by this problem.

Severity

Affected Versions

  • Filesystem Trigger Plugin up to and including 0.40
  • Markdown Formatter Plugin up to and including 0.1.0
  • Nuget Plugin up to and including 1.0
  • URLTrigger Plugin up to and including 0.48

Fix

  • Filesystem Trigger Plugin should be updated to version 0.41
  • Markdown Formatter Plugin should be updated to version 0.2.0
  • Nuget Plugin should be updated to version 1.1
  • URLTrigger Plugin should be updated to version 0.49

These versions include fixes to the vulnerabilities described above. All prior versions are considered to be affected by these vulnerabilities unless otherwise indicated.

Credit

The Jenkins project would like to thank the reporters for discovering and reporting these vulnerabilities:

  • Kevin Guerroudj for SECURITY-2339, SECURITY-2340, SECURITY-2341