CVE-2023-43655 | Remote Code Execution via web-accessible composer.phar

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.ini, and avoid publishing composer.phar to the web as this is not best practice.

Published: 2023-09-29 Last update: 2025-04-23 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2023-43655 is rated Moderate Risk (54.2/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.53%). Mandatory action: Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-43655

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-09 1.57% 1.53% -0.04%
2 2026-05-27 1.18% 1.57% +0.40%
3 2026-05-24 1.18%

Full EPSS history (37 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-43655

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
0.5 5.9 [email protected]
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
2.8 5.9 [email protected]

Weakness enumeration for CVE-2023-43655

GitHub Security Advisory for CVE-2023-43655

GHSA-jm6m-4632-36hf · Severity: high · Ecosystem: composer — Composer Remote Code Execution vulnerability via web-accessible composer.phar

OS Trackers for CVE-2023-43655

vendor priority summary link
alpine CVE-2023-43655: 1 source package rows (composer); 12 state rows across 6 repos (3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 6, open 6. https://security.alpinelinux.org/vuln/CVE-2023-43655
debian not yet assigned CVE-2023-43655 not yet assigned priority: Debian including 1 source packages (composer), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2023-43655
gentoo normal CVE-2023-43655: 1 GLSA(s) (202508-06), 1 atom(s) (dev-php/composer); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2023-43655
suse medium CVE-2023-43655 severity moderate: SUSE including 4 source package names (latest:php-composer2-2.2.3-150400.3.6.1, php-composer2-2.2.3-150400.3.6.1, php-composer2-2.6.4-1.1, php-composer2-2.8.9-160000.2.2), 10 product×package rows across 10 product lines (Container bci/php, Container bci/php-apache, … (10 product lines)): Fixed 10. https://www.suse.com/security/cve/CVE-2023-43655/
ubuntu medium CVE-2023-43655 medium priority: Ubuntu including 1 source packages (composer), 12 status rows across 12 suites (bionic, focal, jammy, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): released 5, not-affected 4, ignored 3. https://ubuntu.com/security/CVE-2023-43655

Affected software / configurations for CVE-2023-43655

Vendor Product Version Raw CPE
getcomposer composer < 1.10.27 cpe:2.3:a:getcomposer:composer:*:*:*:*:*:*:*:*
getcomposer composer >= 2.0.0, < 2.2.21 cpe:2.3:a:getcomposer:composer:*:*:*:*:*:*:*:*
getcomposer composer >= 2.3.0, < 2.6.4 cpe:2.3:a:getcomposer:composer:*:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
fedoraproject fedora 37 cpe:2.3:o:fedoraproject:fedora:37:*:*:*:*:*:*:*
fedoraproject fedora 38 cpe:2.3:o:fedoraproject:fedora:38:*:*:*:*:*:*:*

References for CVE-2023-43655

URL Tags
https://github.com/composer/composer/commit/4fce14795aba98e40b6c4f5047305aba17a6120d Patch
https://github.com/composer/composer/commit/955a48e6319c8962e5cd421b07c00ab3c728968c Patch
https://github.com/composer/composer/commit/95e091c921037b7b6564942845e7b738f6b95c9c Patch
https://github.com/composer/composer/security/advisories/GHSA-jm6m-4632-36hf Vendor Advisory
https://lists.debian.org/debian-lts-announce/2024/03/msg00030.html Mailing List
https://lists.fedoraproject.org/archives/list/[email protected]/message/66H2WKFUO255T3BZTL72TNYJYH2XM5FG/ Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/7AWYAUZNH565NWPIKGEIYBWHYNM5JGAE/ Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/KFOPGPW2KS37O3KJWBRGTUWHTXCQXBS2/ Mailing List Third Party Advisory
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