CVE-2026-40261: Composer is a dependency manager for PHP

This month

HIGH 8.8UPGRADE

CVE-2026-40261 is a high-severity flaw (CVSS 8.8) affecting composer. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Composer is a dependency manager for PHP. Versions 1.0 through 2.2.26 and 2.3 through 2.9.5 contain a command injection vulnerability in the Perforce::syncCodeBase() method, which appends the $sourceReference parameter to a shell command without proper escaping, and additionally in the Perforce::generateP4Command() method as in GHSA-wg36-wvj6-r67p / CVE-2026-40176, which interpolates user-supplied Perforce connection parameters (port, user, clien

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Weakness	CWE-20, CWE-78
Published	2026-04-15
Last modified	2026-07-15

Publisher (CNA): GitHub, Inc. · Vendor: getcomposer

Last updated 2026-07-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-15 21:17 UTCPublished CVE record published
2026-07-15 02:21 UTCUpdated Record last modified

getcomposer composer UPGRADE

Affected: >= 1.0.0 and <= 2.2.26 · >= 2.3.0 and <= 2.9.5

Fixed in: newer than 2.9.5

Safe to downgrade to: a release before 1.0.0

1. Check installed version

apt-cache policy composer || rpm -q composer || composer --version

2. UPGRADE to newer than 2.9.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade composer

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade composer

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison composer sudo apt install composer=<VERSION_BEFORE_1.0.0> sudo apt-mark hold composer

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list composer sudo dnf downgrade composer-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add composer

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40261?

composer: upgrade to newer than 2.9.5. Exact commands for each OS are on this page.

Is CVE-2026-40261 being exploited?

CVE-2026-40261 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40261 affect?

CVE-2026-40261 affects composer. Severity is high (CVSS 8.8). Composer is a dependency manager for PHP. Versions 1.0 through 2.2.26 and 2.3 through 2.9.5 contain a command injection vulnerability in the Perforce::syncCodeBase() method, which appends the $sourceReference parameter to a shell command wi

How urgent is CVE-2026-40261?

Priority 50/100. High severity

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-40176 HIGH 7.8 UPGRADE Composer is a dependency manager for PHP

References

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