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TI-2026-48553 Aliases CVE-2026-69209

Http4s: WebSocket decoder accepts unbounded message sizes

Priority MEDIUM 40CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-400.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0063 50th percentileScored 2026-11-07
Fix Fixed http4s (http4s): 0.23.35, 1.0.0-M47

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
http4shttp4sbefore 0.23.35; 1.0.0-M1 to before 1.0.0-M470.23.35, 1.0.0-M47Patch availableCNA
  • http4s Vendorhttp4s Affected before 0.23.35; 1.0.0-M1 to before 1.0.0-M47 Fixed in 0.23.35, 1.0.0-M47 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:typelevel:http4s:*:*:*:*:*:*:*:*——http4s
  • cpe:2.3:a:typelevel:http4s:*:*:*:*:*:*:*:* Versions — — ·http4s

Remediation

  • Fix · CNA http4s (http4s) Fixed in 0.23.35, 1.0.0-M47

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-69209
  2. 2026-10-28 EPSS moved to the 50th–90th percentile

References

Other 4

  • TI-2022-13223 mTLS client verification is skipped in fs2 on Node.js CVSS 3.1CRITICAL 9.8
  • TI-2023-08714 Http4s has fatal error parsing User-Agent and Server headers CVSS 3.1HIGH 7.5
  • TI-2022-06031 Hash collision in typelevel jawn CVSS 3.1HIGH 7.5
  • TI-2025-37261 Http4s vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section CVSS 4.0MEDIUM 6.3
  • TI-2026-44185 http4s-scala-xml has an XML External Entity (XXE) processing issue CVSS 3.1CRITICAL 9.3
  • TI-2020-04336 Local file inclusion vulnerability in http4s CVSS 3.1HIGH 7.6
See all 36 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences