Composer: Malicious Package Can Make Private Files World-Readable

Published as "Composer: Path traversal in package bin field lets dependencies chmod arbitrary host files"

medium Composer · Last reviewed Nov 3, 2026

CVE: CVE-2026-59946
GHSA: GHSA-gjfg-22fp-rrxx
Packagist: PKSA-q3ht-3g42-rg8f
Reported: Jul 20, 2026

Lets a malicious dependency change permissions on files outside its folder, making private files such as SSH keys readable by other users.

Affected and fixed versions

In composer/composer. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
2.3.0 – 2.10.1	2.10.2	Supported

Show 1 older branch, no longer supported

1.0.0 – 2.2.28

2.2.29

Upgrade

Run the line for the branch you are on.

composer require composer/composer:^2.10.2

What this means

A malicious or compromised package can make Composer change the permissions of a file outside the package's own folder during composer install, update or require. The file becomes readable and runnable by everyone on the machine. A private file, like an SSH key, can then be read by other users.

The Composer advisory says it doesn't read, change or run the file, and it isn't remote code execution. Composer found no sign of any package on Packagist.org using it.

Who is affected

Projects that depend, even indirectly, on a package you don't fully trust, installed on a machine that holds private files Composer's user can change. Examples include SSH keys, .env files and ~/.aws/credentials. --no-scripts, --no-plugins and allow-plugins don't block it. Run as root, as in many CI containers, any file on the system can be affected.

What to do

Update composer/composer to 2.10.2, or to 2.2.29 if you stay on 2.2. Composer 1.x won't get a fix, so move to 2.x. The fix rejects packages whose binaries point outside their folder. Composer says upgrading is the only complete fix.

A way around this fix was found later. See GHSA-96h3-5x6v-m776, fixed in 2.10.3 and 2.2.30, and update to those.

Reported by iliaal.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Composer: Malicious Package Can Make Private Files World-Readable (CVE-2026-59946, GHSA-gjfg-22fp-rrxx)
Details: https://phpnews.net/security/composer/ghsa-gjfg-22fp-rrxx

Affected versions, as Composer constraints:
- composer/composer: >=1.0.0,<2.2.29|>=2.3.0,<2.10.2

Fixed releases on branches that still get security fixes:
- 2.3.0 – 2.10.1: update to 2.10.2

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/composer/ghsa-gjfg-22fp-rrxx and check whether the project meets the conditions it describes (a feature in use, a config value, a driver). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

← All Composer advisories