CVE-2021-29472: Composer is a dependency manager for PHP. URLs for Mercurial repositories in the root composer.json and package source download URLs are not sanitized...

Description

Composer is a dependency manager for PHP. URLs for Mercurial repositories in the root composer.json and package source download URLs are not sanitized correctly. Specifically crafted URL values allow code to be executed in the HgDriver if hg/Mercurial is installed on the system. The impact to Composer users directly is limited as the composer.json file is typically under their own control and source download URLs can only be supplied by third party Composer repositories they explicitly trust to download and execute source code from, e.g. Composer plugins. The main impact is to services passing user input to Composer, including Packagist.org and Private Packagist. This allowed users to trigger remote code execution. The vulnerability has been patched on Packagist.org and Private Packagist within 12h of receiving the initial vulnerability report and based on a review of logs, to the best of our knowledge, was not abused by anyone. Other services/tools using VcsRepository/VcsDriver or derivatives may also be vulnerable and should upgrade their composer/composer dependency immediately. Versions 1.10.22 and 2.0.13 include patches for this issue.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

4.81%

90.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Getcomposer	Composer	< 1.10.22
Getcomposer	Composer	>= 2.0, < 2.0.13
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34

References

https://blog.sonarsource.com/php-supply-chain-attack-on-composer/Exploit, Third Party Advisory
https://getcomposer.org/Vendor Advisory
https://github.com/composer/composer/security/advisories/GHSA-h5h8-pc6h-jvvxThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00009.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FAQUAMGO4Q4BLNZ2OH4CXQD7UK4IO2GE/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KN3DMFH42BJW45VT6FYF2RXKC26D6VC2/
https://www.debian.org/security/2021/dsa-4907Third Party Advisory
https://blog.sonarsource.com/php-supply-chain-attack-on-composer/Exploit, Third Party Advisory
https://getcomposer.org/Vendor Advisory
https://github.com/composer/composer/security/advisories/GHSA-h5h8-pc6h-jvvxThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00009.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FAQUAMGO4Q4BLNZ2OH4CXQD7UK4IO2GE/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KN3DMFH42BJW45VT6FYF2RXKC26D6VC2/
https://www.debian.org/security/2021/dsa-4907Third Party Advisory

Timeline

Published: Apr 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-29472?

Composer is a dependency manager for PHP. URLs for Mercurial repositories in the root composer.json and package source download URLs are not sanitized correctly. Specifically crafted URL values allow code to be executed in the HgDriver if hg/Mercurial is installed on the system. The impact to Composer users directly is limited as the composer.json file is typically under their own control and source download URLs can only be supplied by third party Composer repositories they explicitly trust to download and execute source code from, e.g. Composer plugins. The main impact is to services passing user input to Composer, including Packagist.org and Private Packagist. This allowed users to trigger remote code execution. The vulnerability has been patched on Packagist.org and Private Packagist within 12h of receiving the initial vulnerability report and based on a review of logs, to the best of our knowledge, was not abused by anyone. Other services/tools using VcsRepository/VcsDriver or derivatives may also be vulnerable and should upgrade their composer/composer dependency immediately. Versions 1.10.22 and 2.0.13 include patches for this issue.

How severe is CVE-2021-29472?

CVE-2021-29472 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 4.81% probability of exploitation in the next 30 days.

How do I fix CVE-2021-29472?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.