What’s Vulnerable › Vulnerabilities

CVE-2025-58369: fs2: Half-shutdown of socket during TLS handshake may result in spin loop on opposite side

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-09-05 · updated 2026-10-01
• Weakness: CWE-400

Description

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.

Affected products

• typelevel fs2: from 3.0.0-M1, < 3.12.2; from 3.13.0-M1, < 3.13.0-M7; before 2.5.13

References

• https://github.com/typelevel/fs2/commit/46e2dc3abf994dcf3d0b804b2ddb3c10c04d4976
• https://github.com/typelevel/fs2/commit/5c6c4c6c1ef330f7e6b53661ecc63d5f5ba8885c
• https://github.com/typelevel/fs2/commit/edf0c4f2e660360d1c1a8c5377ce32294de89238
• https://github.com/typelevel/fs2/issues/3590
• https://github.com/typelevel/fs2/releases/tag/v3.12.2
• https://github.com/typelevel/fs2/releases/tag/v3.13.0-M7
• https://github.com/typelevel/fs2/security/advisories/GHSA-rrw2-px9j-qffj

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