Summary
Composer before 2016-02-10 allows cache poisoning from other projects built on the same host. This results in attacker-controlled code entering a server-side build process. The issue occurs because of the way that dist packages are cached. The cache key is derived from the package name, the dist type, and certain other data from the package repository (which may simply be a commit hash, and thus can be found by an attacker). Versions through 1.0.0-alpha11 are affected, and 1.0.0 is unaffected.
Impact
CVE-2015-8371 has a CVSS score of 8.8 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.0.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2015-8371? CVE-2015-8371 is a high-severity security vulnerability in composer/composer (composer), affecting versions <= 1.0.0-alpha11. It is fixed in 1.0.0.
- How severe is CVE-2015-8371? CVE-2015-8371 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of composer/composer are affected by CVE-2015-8371? composer/composer (composer) versions <= 1.0.0-alpha11 is affected.
- Is there a fix for CVE-2015-8371? Yes. CVE-2015-8371 is fixed in 1.0.0. Upgrade to this version or later.
- Is CVE-2015-8371 exploitable, and should I be worried? Whether CVE-2015-8371 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2015-8371 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2015-8371? Upgrade
composer/composerto 1.0.0 or later.