CVE-2026-59946 composer CVE debrief

Who should care

Developers and administrators using Composer for dependency management in PHP projects should be aware of this vulnerability and take steps to mitigate it. This includes updating to a patched version of Composer and reviewing package bin entries for potential vulnerabilities. Affected operator, platform, vulnerability-management, and security-team impact should be reviewed.

Technical summary

The vulnerability occurs when a Composer package bin entry contains .. path segments, allowing an attacker to resolve outside the package install directory. This can cause Composer's binary installation flow to chmod an existing host file to a world-readable and world-executable mode during composer install, update, or require. The issue is fixed in versions 2.2.29 and 2.10.2. Affected product deployments should be reviewed for potential exposure, and compensating controls should be considered while remediation is scheduled.

Defensive priority

Medium

Recommended defensive actions

• Update to a patched version of Composer (2.2.29 or 2.10.2)
• Review package bin entries for potential vulnerabilities
• Monitor for suspicious activity in Composer installations
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The vulnerability was reported in the NVD database and has a CVSS score of 6.1. The issue is fixed in versions 2.2.29 and 2.10.2 of Composer. To verify, defenders should review package bin entries for potential vulnerabilities and monitor for suspicious activity in Composer installations. Evidence is limited, and further verification is required to confirm affected scope and severity.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.