Public proof of conceptFix available

CVE-2026-46420

Q: Is CVE-2026-46420 actively exploited?

Active exploitation of CVE-2026-46420 has not been confirmed. Its EPSS score was 2.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-46420?

CVE-2026-46420 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2026-07-17
Fixed in2.37.1
WeaknessCWE-78

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

setup-php is a GitHub action to set up PHP with extensions, php.ini configuration, coverage drivers, and tools. From 2.25.0 prior to 2.37.1, shivammathur/setup-php resolves the PHP version from repository-controlled files such as .php-version, composer.lock through platform-overrides.php, and composer.json through config.platform.php, and insufficiently constrains those values before incorporating them into generated shell or PowerShell setup scripts, allowing command injection on a GitHub Actions runner when workflows such as pull_request_target check out attacker-controlled contents before invoking setup-php. This issue is fixed in version 2.37.1.

Timeline

dates in UTC

2026-07-1720:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-46420?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-46420?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Shivammathur setup php

Branch	Affected	Fixed in	Source
2.x	≥ 2.25.0, < 2.37.1	2.37.1	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Shivammathur setup php to 2.37.1

Advisories and patches

github.comPatch
github.comRelease Notes
github.comPatch · Vendor Advisory

Detection

read 2026-10-23 19:25 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedJvr2022/CVE-2026-46420

Sources

CISA-ADPSSVC decisionnone2026-07-20
OpenCVESSVC decisionnone—
CNACVSS 3.15.6read 2026-10-23
NVDCVSS 3.19.8read 2026-10-23
CNAweakness (CWE)CWE-78read 2026-10-23
FIRST EPSSEPSS score2.0 %2026-10-23
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2026-07-17
Last Modified: 2026-08-18
NVD status: Analyzed

Frequently asked questions

What is CVE-2026-46420?

Is CVE-2026-46420 actively exploited?

Active exploitation of CVE-2026-46420 has not been confirmed. Its EPSS score was 2.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-46420?

CVE-2026-46420 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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