CVE-2026-69209 (GCVE-0-2026-69209)
Vulnerability from cvelistv5 – Published: 2026-09-15 18:55 – Updated: 2026-09-16 18:37
VLAI
EPSS
VEX
Title
Http4s: WebSocket decoder accepts unbounded message sizes
Summary
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The shared WebSocket decoder permits unbounded message buffering because defragmentation accumulates fragments without a limit and FrameTranscoder accepts declared lengths up to Int.MaxValue. A remote client that completes a WebSocket handshake against an http4s-blaze-server or http4s-ember-server endpoint can exhaust server memory with oversized frames or fragmented messages. The patched decoder applies a configurable 64 MiB default limit to individual frames and defragmented messages through EmberServerBuilder.withMaxWebSocketMessageSize. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
Severity
7.5 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 18:25 UTC
CWE
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/http4s/http4s/security/advisor… | x_refsource_CONFIRM |
| https://github.com/http4s/http4s/commit/d578c3c9d… | x_refsource_MISC |
| https://github.com/http4s/http4s/releases/tag/v0.23.35 | x_refsource_MISC |
| https://github.com/http4s/http4s/releases/tag/v1.… | x_refsource_MISC |
Impacted products
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| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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