How severe is CVE-2025-58369?

CVE-2025-58369 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2025-58369?

CVE-2025-58369 affects the following packages: co.fs2:fs2-io_2.12 (Maven), co.fs2:fs2-io_2.12 (Maven), co.fs2:fs2-io_2.13 (Maven), co.fs2:fs2-io_2.13 (Maven), co.fs2:fs2-io_3 (Maven), co.fs2:fs2-io_3 (Maven), co.fs2:fs2-io_0.26 (Maven), co.fs2:fs2-io_0.27 (Maven), and 9 more. Ecosystems affected: Maven.

How do I fix CVE-2025-58369?

Update co.fs2:fs2-io_2.12 to 3.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-58369 is resolved across your whole dependency graph.

How do I detect CVE-2025-58369 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for co.fs2:fs2-io_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-58369 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2025-58369 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-58369 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-58369?

CVE-2025-58369 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 39th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-58369?

CVE-2025-58369 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-58369 published, and has it been updated?

CVE-2025-58369 was published on September 5, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2025-58369 — fs2-io_2.12

MEDIUMFix: typelevel/fs2@46e2dc3

CVE-2025-58369 is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in co.fs2:fs2-io_2.12. A fix is available for co.fs2:fs2-io_2.12 — see the affected versions and patch details below.

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

Also known asGHSA-rrw2-px9j-qffj

Published

Sep 5, 2025

Updated

Oct 28, 2026

Affected

17 pkgs

Patched

9 / 17

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-58369.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

17 pkgs affected

☕co.fs2:fs2-io_2.12☕co.fs2:fs2-io_2.12☕co.fs2:fs2-io_2.13☕co.fs2:fs2-io_2.13☕co.fs2:fs2-io_3☕co.fs2:fs2-io_3☕co.fs2:fs2-io_0.26☕co.fs2:fs2-io_0.27+9 more

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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 Packages

17 total 9 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`co.fs2:fs2-io_2.12`	≥ 3.0.0-M1&&< 3.12.2	3.12.2`co.fs2:fs2-io_2.12:3.12.2`
☕Maven	`co.fs2:fs2-io_2.12`	≥ 3.13.0-M1&&< 3.13.0-M7	3.13.0-M7`co.fs2:fs2-io_2.12:3.13.0-M7`
☕Maven	`co.fs2:fs2-io_2.13`	≥ 3.0.0-M1&&< 3.12.2	3.12.2`co.fs2:fs2-io_2.13:3.12.2`
☕Maven	`co.fs2:fs2-io_2.13`	≥ 3.13.0-M1&&< 3.13.0-M7	3.13.0-M7`co.fs2:fs2-io_2.13:3.13.0-M7`
☕Maven	`co.fs2:fs2-io_3`	≥ 3.0.0-M1&&< 3.12.2	3.12.2`co.fs2:fs2-io_3:3.12.2`
☕Maven	`co.fs2:fs2-io_3`	≥ 3.13.0-M1&&< 3.13.0-M7	3.13.0-M7`co.fs2:fs2-io_3:3.13.0-M7`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for co.fs2:fs2-io_2.12, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update co.fs2:fs2-io_2.12 to 3.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-58369 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### 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