Resource exhaustion in Typelevel Fs2

CVE-2025-58369

fs2 is a compositional, streaming I/O library for Scala. Versions up to and including 2.5.12, 3.0.0-M1 through 3.12.2, and 3.13.0-M1 through 3.13.0-M6 are vulnerable to denial of service attacks though TLS sessions using fs2-io on the JVM using the fs2.io.net.tls package. When establishing a TLS session, 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. The CPU is consumed until the overall connection is closed, potentially shutting down a fs2-io powered server. This issue is fixed in versions 2.5.13, 3.12.1, and 3.13.0-M7.

Vulnerability class: DoS (Denial of Service)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.004 (34.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 34.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2025-58369: held from 0.004 to 0.004.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

  • Typelevel Fs2 — versions >= 3.0.0-M1, < 3.12.2, >= 3.13.0-M1, < 3.13.0-M7, < 2.5.13

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2025-58369?
CVE-2025-58369 is a medium-severity vulnerability in Typelevel Fs2, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2025-09-05.
How severe is CVE-2025-58369?
Medium severity. CVSS v3 base score is 5.3 out of 10.