Command Injection Vulnerability in Mechanize

Exploitation

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

CVSS

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

EPSS

• CVE-2021-21289: 3.55% estimated exploitation activity in the next 30 days; percentile 89.32 (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.

This security advisory has been created for public disclosure of a Command Injection vulnerability that was responsibly reported by @kyoshidajp (Katsuhiko YOSHIDA). Impact Mechanize = v2.0, < v2.7.7 allows for OS commands to be injected using several classes' methods which implicitly use Ruby's Kernel.open method. Exploitation is possible only if untrusted input is used as a local filename and passed to any of these calls: - Mechanize::CookieJar#load: since v2.0 (see 208e3ed) - Mechanize::CookieJar#saveas: since v2.0 (see 5b776a4) - Mechanize#download: since v2.2 (see dc91667) - Mechanize::Download#save and #save! since v2.1 (see 98b2f51, bd62ff0) - Mechanize::File#save and #saveas: since v2.1 (see 2bf7519) - Mechanize::FileResponse#readbody: since v2.0 (see 01039f5) Patches These vulnerabilities are patched in Mechanize v2.7.7. Workarounds No workarounds are available. We recommend upgrading to v2.7.7 or later. References See…

Published by the source

2 Feb 2021, 18:50 UTC

Last modified by the source

4 May 2023, 19:54 UTC

Source last checked

26 Oct 2026, 15:47 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-qrqm-fpv6-6r8g

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# Patch Next advisory brief: CVE-2021-21289

Advisory: Command Injection Vulnerability in Mechanize
IDs: CVE-2021-21289, GHSA-qrqm-fpv6-6r8g
Record: https://patchnext.com/advisories/cve-2021-21289 (revision 1, source checked 26 Oct 2026, 15:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mechanize 2.7.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems mechanize: affected >= 2.0.0, < 2.7.7; fixed in 2.7.7

## Suggested inspection (read-only)
- RubyGems mechanize: 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 mechanize.
- 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-qrqm-fpv6-6r8g (GitHub-reviewed advisory GHSA-qrqm-fpv6-6r8g lists affected ranges: RubyGems mechanize >=2.0.0 <2.7.7)

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