---
id: CVE-2025-58369
title: 'fs2 is a compositional, streaming I/O library for Scala'
summary: >-
  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 JV…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-400
published: '2025-09-05'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T16:10:00.257'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-58369'
references:
  - url: >-
      https://github.com/typelevel/fs2/commit/46e2dc3abf994dcf3d0b804b2ddb3c10c04d4976
    label: security-advisories@github.com
  - url: >-
      https://github.com/typelevel/fs2/commit/5c6c4c6c1ef330f7e6b53661ecc63d5f5ba8885c
    label: security-advisories@github.com
  - url: >-
      https://github.com/typelevel/fs2/commit/edf0c4f2e660360d1c1a8c5377ce32294de89238
    label: security-advisories@github.com
  - url: 'https://github.com/typelevel/fs2/issues/3590'
    label: security-advisories@github.com
  - url: 'https://github.com/typelevel/fs2/releases/tag/v3.12.2'
    label: security-advisories@github.com
  - url: 'https://github.com/typelevel/fs2/releases/tag/v3.13.0-M7'
    label: security-advisories@github.com
  - url: 'https://github.com/typelevel/fs2/security/advisories/GHSA-rrw2-px9j-qffj'
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00427
epssPercentile: 0.34629
ingestedAt: '2026-10-01T18:55:42.283Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.