CVE-2025-58369

Workarounds

No workarounds.

For more information

If you have any questions or comments about this advisory:

Open an issue.
Contact the Typelevel Security Team.

When establishing a TLS session using fs2-io on the JVM using the fs2.io.net.tls package, if one side of the connection shuts down write while the peer side is awaiting more data to progress the TLS handshake, the peer side will spin loop on the socket read, fully utilizing a CPU. This CPU is consumed until the overall connection is closed.

This could be used as a denial of service attack on an fs2-io powered server -- for example, by opening many connections and putting them in a half-shutdown state.

Note: this issue impacts ember backed http4s servers with HTTPS as a result of ember using fs2's TLS support.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2025-58369 has a CVSS score of 5.3 (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 (3.13.0-M7, 3.12.2, 2.5.13); upgrading removes the vulnerable code path.

Kodem intelligence

Fixed in fs2 3.12.2 and 3.13.0-M7.

1. What is CVE-2025-58369? CVE-2025-58369 is a medium-severity uncontrolled resource consumption vulnerability in co.fs2:fs2-io_2.12 (maven), affecting versions >= 3.13.0-M1, < 3.13.0-M7. It is fixed in 3.13.0-M7, 3.12.2, 2.5.13. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2025-58369? CVE-2025-58369 has a CVSS score of 5.3 (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 packages are affected by CVE-2025-58369?
   • co.fs2:fs2-io_2.12 (maven) (versions >= 3.13.0-M1, < 3.13.0-M7)
   • co.fs2:fs2-io_2.13 (maven) (versions >= 3.13.0-M1, < 3.13.0-M7)
   • co.fs2:fs2-io_3 (maven) (versions >= 3.13.0-M1, < 3.13.0-M7)
   • co.fs2:fs2-io_0.26 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_0.27 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_2.11 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_2.12.0-M4 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_2.12.0-RC1 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_2.12.0-M5 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_2.12.0-RC2 (maven) (versions < 2.5.13)
   • co.fs2:fs2-io_2.13.0-M5 (maven) (versions < 2.5.13)
4. Is there a fix for CVE-2025-58369? Yes. CVE-2025-58369 is fixed in 3.13.0-M7, 3.12.2, 2.5.13. Upgrade to this version or later.
5. Is CVE-2025-58369 exploitable, and should I be worried? Whether CVE-2025-58369 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-2025-58369 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-2025-58369?
   • Upgrade co.fs2:fs2-io_2.12 to 3.13.0-M7 or later
   • Upgrade co.fs2:fs2-io_2.13 to 3.13.0-M7 or later
   • Upgrade co.fs2:fs2-io_3 to 3.13.0-M7 or later
   • Upgrade co.fs2:fs2-io_2.12 to 3.12.2 or later
   • Upgrade co.fs2:fs2-io_2.13 to 3.12.2 or later
   • Upgrade co.fs2:fs2-io_3 to 3.12.2 or later
   • Upgrade co.fs2:fs2-io_2.12 to 2.5.13 or later
   • Upgrade co.fs2:fs2-io_2.13 to 2.5.13 or later
   • Upgrade co.fs2:fs2-io_3 to 2.5.13 or later