CVE-2020-11077 is a medium-severity security vulnerability in puma (rubygems), affecting versions < 3.12.6. It is fixed in 3.12.6, 4.3.5.
Impact This is a similar but different vulnerability to the one patched in 3.12.5 and 4.3.4. A client could smuggle a request through a proxy, causing the proxy to send a response back to another unknown client. If the proxy uses persistent connections and the client adds another request in via HTTP pipelining, the proxy may mistake it as the first request's body. Puma, however, would see it as two requests, and when processing the second request, send back a response that the proxy does not expect. If the proxy has reused the persistent connection to Puma to send another request for a different client, the second response from the first client will be sent to the second client. Patches The problem has been fixed in Puma 3.12.6 and Puma 4.3.5. For more information If you have any questions or comments about this advisory: Open an issue in Puma See our security policy
CVE-2020-11077 has a CVSS score of 6.8 (Medium). 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 (3.12.6, 4.3.5). Upgrading removes the vulnerable code path.
rubygems
puma (< 3.12.6)puma (>= 4.0.0, < 4.3.5)puma → 3.12.6 (rubygems)puma → 4.3.5 (rubygems)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 instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2020-11077 is reachable in your applications. Explore open-source security for your team.
See if CVE-2020-11077 is reachable in your applications. Get a demo
Upgrade the following packages to resolve this vulnerability:
puma to 3.12.6 or laterpuma to 4.3.5 or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2020-11077 is a medium-severity security vulnerability in puma (rubygems), affecting versions < 3.12.6. It is fixed in 3.12.6, 4.3.5.
CVE-2020-11077 has a CVSS score of 6.8 (Medium). 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.
puma (rubygems) versions < 3.12.6 is affected.
Yes. CVE-2020-11077 is fixed in 3.12.6, 4.3.5. Upgrade to this version or later.
Whether CVE-2020-11077 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
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.
puma to 3.12.6 or laterpuma to 4.3.5 or later