CVE-2019-16779

In RubyGem excon, interrupted Persistent Connections May Leak Response Data

Workarounds

Users can workaround the problem by disabling persistent connections, though this may cause performance implications.

References

See the patch for further details.

For more information

If you have any questions or comments about this advisory:

• Open an issue in excon/issues
• Email us at [email protected]

There was a race condition around persistent connections, where a connection which is interrupted (such as by a timeout) would leave data on the socket. Subsequent requests would then read this data, returning content from the previous response. The race condition window appears to be short, and it would be difficult to purposefully exploit this.

Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing. Typical impact: TOCTOU exploits, data corruption, or privilege escalation.

CVE-2019-16779 has a CVSS score of 5.8 (Medium). The vector is network-reachable, low 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 (0.71.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

The problem has been patched in 0.71.0, users should upgrade to this or a newer version (if one exists).

1. What is CVE-2019-16779? CVE-2019-16779 is a medium-severity race condition vulnerability in excon (rubygems), affecting versions < 0.71.0. It is fixed in 0.71.0. Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing.
2. How severe is CVE-2019-16779? CVE-2019-16779 has a CVSS score of 5.8 (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.
3. Which versions of excon are affected by CVE-2019-16779? excon (rubygems) versions < 0.71.0 is affected.
4. Is there a fix for CVE-2019-16779? Yes. CVE-2019-16779 is fixed in 0.71.0. Upgrade to this version or later.
5. Is CVE-2019-16779 exploitable, and should I be worried? Whether CVE-2019-16779 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
6. What actually determines whether CVE-2019-16779 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.
7. How do I fix CVE-2019-16779? Upgrade excon to 0.71.0 or later.

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