FS2 half-shutdown of socket during TLS handshake may result in spin loop on opposite side
Impact
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.
Patches
Fixed in fs2 3.12.2 and 3.13.0-M7.
Workarounds
No workarounds.
For more information
If you have any questions or comments about this advisory:
Open an issue. Contact the Typelevel Security Team.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | co.fs2:fs2-io_0.26 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_0.27 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.11 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.12 | >= 3.0.0-M1, < 3.12.2, >= 3.13.0-M1, < 3.13.0-M7, < 2.5.13 | 3.12.2, 3.13.0-M7, 2.5.13 |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.12.0-M4 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.12.0-M5 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.12.0-RC1 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.12.0-RC2 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.13 | >= 3.0.0-M1, < 3.12.2, >= 3.13.0-M1, < 3.13.0-M7, < 2.5.13 | 3.12.2, 3.13.0-M7, 2.5.13 |
| Java / Kotlin (Maven) | co.fs2:fs2-io_2.13.0-M5 | all versions | no fix |
| Java / Kotlin (Maven) | co.fs2:fs2-io_3 | >= 3.0.0-M1, < 3.12.2, >= 3.13.0-M1, < 3.13.0-M7, < 2.5.13 | 3.12.2, 3.13.0-M7, 2.5.13 |
References
- https://github.com/typelevel/fs2/security/advisories/GHSA-rrw2-px9j-qffj
- https://nvd.nist.gov/vuln/detail/CVE-2025-58369
- https://github.com/typelevel/fs2/issues/3590
- https://github.com/typelevel/fs2/pull/3624
- 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
- https://github.com/typelevel/fs2/releases/tag/v3.12.2
- https://github.com/typelevel/fs2/releases/tag/v3.13.0-M7
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L- Weakness (CWE)
CWE-400- Platform
- Java / Kotlin (Maven)
- Package
co.fs2:fs2-io_0.26, co.fs2:fs2-io_0.27, co.fs2:fs2-io_2.11- Disclosed
- 05.09.2025
- Updated
- 11.10.2026 12:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-rrw2-px9j-qffj - CC BY 4.0
Vulnerability history: co.fs2:fs2-io_2.11
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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