Server interruption via TLS read spin loop
Published Sep 5, 2025 · Updated Nov 7, 2025
Denial of service in Typelevel FS2 fs2-io allows remote attackers to exhaust server CPU via half-closed TLS handshakes. TLSEngine's unwrapHandshake path treats an end-of-stream read with buffered input as a successful no-op instead of stopping the unwrap operation, causing repeated socket reads. Unauthenticated network access to an fs2-io TLS endpoint is sufficient; multiple half-shutdown connections can consume CPU until they close and interrupt an affected server.
Summary
What happened
Denial of service in Typelevel FS2 fs2-io allows remote attackers to exhaust server CPU via half-closed TLS handshakes. TLSEngine's unwrapHandshake path treats an end-of-stream read with buffered input as a successful no-op instead of stopping the unwrap operation, causing repeated socket reads. Unauthenticated network access to an fs2-io TLS endpoint is sufficient; multiple half-shutdown connections can consume CPU until they close and interrupt an affected server.
The record
- CVE
- CVE-2025-58369
- Published
- Sep 5, 2025
- Updated
- Nov 7, 2025
- Vendor
- Typelevel
- Product
- FS2
- Classifications
- CWE-400, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 5, 2025CVE publishedPublication date reported by the CVE source.
- Nov 7, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.5.13
- Affected versionversion=>= 3.0.0-M1, < 3.12.2
- Affected versionversion=>= 3.13.0-M1, < 3.13.0-M7
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo