Summary
Workarounds
Apply https://github.com/octobercms/library/commit/642f597489e6f644d4bd9a0c267e864cabead024 to your installation manually if unable to upgrade to Build 472 or v1.1.2.
References
- Reported by Anisio (Brazilian Information Security Analyst)
- http://cve.circl.lu/cve/CVE-2021-3311
For more information
If you have any questions or comments about this advisory:
- Email us at [email protected]
Threat assessment:
Impact
When logging out, the session ID was not invalidated. This is not a problem while the user is logged out, but as soon as the user logs back in the old session ID would be valid again; which means that anyone that gained access to the old session cookie would be able to act as the logged in user. This is not a major concern for the majority of cases, since it requires a malicious party gaining access to the session cookie in the first place, but nevertheless has been fixed.
CVE-2021-3311 has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. 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 (1.0.472, 1.1.2); 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
Issue has been patched in Build 472 (v1.0.472) and v1.1.2.
Frequently Asked Questions
- What is CVE-2021-3311? CVE-2021-3311 is a critical-severity security vulnerability in october/rain (composer), affecting versions < 1.0.472. It is fixed in 1.0.472, 1.1.2.
- How severe is CVE-2021-3311? CVE-2021-3311 has a CVSS score of 9.8 (Critical). 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 october/rain are affected by CVE-2021-3311? october/rain (composer) versions < 1.0.472 is affected.
- Is there a fix for CVE-2021-3311? Yes. CVE-2021-3311 is fixed in 1.0.472, 1.1.2. Upgrade to this version or later.
- Is CVE-2021-3311 exploitable, and should I be worried? Whether CVE-2021-3311 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-2021-3311 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-2021-3311?
- Upgrade
october/rainto 1.0.472 or later - Upgrade
october/rainto 1.1.2 or later
- Upgrade