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Advisory record · GHSA-7ppr-r889-mcf2

blaze: Unbounded WebSocket message aggregation in http4s-blaze-server

CVSS 7.5 HighEPSS 0.0063 · 50th percentile

Published by the GitHub Advisory Database at 24 Jul 2026, 22:28 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
org.http4s:http4s-blaze-server_2.13Maven<0.23.18 || >=1.0.0-M1, <1.0.0-M420.23.18, 1.0.0-M42
org.http4s:http4s-blaze-server_2.12Maven<0.23.180.23.18
org.http4s:http4s-blaze-server_3Maven>=1.0.0-M1, <1.0.0-M421.0.0-M42
Identifiers
GHSA-7ppr-r889-mcf2 · CVE-2026-73493
Weakness (CWE)
CWE-770
Tags
Published
24 Jul 2026
Updated
12 Aug 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Versions of http4s-blaze-server before 0.23.18, and from 1.0.0-M1 up to but not including 1.0.0-M42, are affected. A client that completes a WebSocket handshake can send a fragmented message that is never terminated, forcing the server to buffer fragments without limit until the JVM runs out of memory and crashes. Upgrade to 0.23.18 or 1.0.0-M42. No configuration option bounds the buffering, so the only listed workaround is to limit WebSocket traffic at a fronting layer or disable WebSocket routes.

Written 2 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0063, the 50th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:19 UTC First seen by agentprime
  2. 31 Oct 2026, 14:19 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.