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GHSA-rrw2-px9j-qffj

MediumCVSS 5.3 / 10
Published Sep 5, 2025·Last modified Nov 7, 2025
Affected Components(0)

No affected components available

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.

Risk Scores
Base Score
5.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the availability of the system.

Threat Intelligence
4.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.40%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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