CVE-2023-43655: Composer is a dependency manager for PHP

This month

MEDIUM 6.4WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2023-43655 is a medium-severity flaw (CVSS 6.4) affecting composer, debian linux, fedora. 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. Users publishing a composer.phar to a public web-accessible server where the composer.phar can be executed as a php file may be subject to a remote code execution vulnerability if PHP also has `register_argc_argv` enabled in php.ini. Versions 2.6.4, 2.2.22 and 1.10.27 patch this vulnerability. Users are advised to upgrade. Users unable to upgrade should make sure `register_argc_argv` is disabled in php.in

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.4 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	High
User interaction	Required
EPSS exploit chance	1.5% (top 25%)
CISA exploited list	No
Weakness	CWE-74
Published	2023-09-29
Last modified	2026-06-17

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

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-09-29 20:15 UTCPublished CVE record published
2026-06-17 06:26 UTCUpdated Record last modified

getcomposer composer UPGRADE

Affected: < 1.10.27 · >= 2.0.0 and < 2.2.21 · >= 2.3.0 and < 2.6.4

Fixed in: 1.10.27, 2.2.21, 2.6.4

Safe to downgrade to: a release before 2.0.0

1. Check installed version

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

2. UPGRADE to 1.10.27 (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 2.0.0 (Debian / Ubuntu)

apt-cache madison composer sudo apt install composer=<VERSION_BEFORE_2.0.0> 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_2.0.0> 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.

debian debian linux MITIGATE

Affected: 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 37 · 38

Fixed in: no fixed release known

Safe to downgrade to: a release before 37

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2023-43655?

composer: upgrade to 1.10.27, 2.2.21, 2.6.4; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-43655 being exploited?

CVE-2023-43655 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-2023-43655 affect?

CVE-2023-43655 affects composer, debian linux, fedora. Severity is medium (CVSS 6.4). Composer is a dependency manager for PHP. Users publishing a composer.phar to a public web-accessible server where the composer.phar can be executed as a php file may be subject to a remote code execution vulnerability if PHP also has `regi

How urgent is CVE-2023-43655?

Priority 46/100. On your watchlist

Software pages

PHP vulnerabilities · Debian vulnerabilities

Related CVEs

CVE-2026-40261 HIGH 8.8 UPGRADE Composer is a dependency manager for PHP
CVE-2026-40176 HIGH 7.8 UPGRADE Composer is a dependency manager for PHP
CVE-2025-67746 MEDIUM 4.3 UPGRADE Composer is a dependency manager for PHP
CVE-2025-3510 MEDIUM 6.4 UPGRADE The tagDiv Composer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via multiple shortcodes
CVE-2024-24821 HIGH 8.8 UPGRADE Composer is a dependency Manager for the PHP language

References

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