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CVE-2026-73493— http4s-blaze-server: Unbounded WebSocket message aggregation

Quick assessment

Affected
http4s blaze
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

http4s blaze是http4s组织的一款Web中间件组件。 http4s blaze 0.23.18之前版本和1.0.0-M42之前版本存在资源管理错误漏洞，该漏洞源于聚合WebSocket消息片段时未限制总大小或片段数量，可能导致服务器JVM堆无界增长，造成拒绝服务。

CVSS 7.5 · High EPSS 0.63% · P49

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 2

VendorProduct Version RangeStatus
http4s blaze < 0.23.18 affected
>= 1.0.0-M1, < 1.0.0-M42 affected
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I. Basic Information for CVE-2026-73493

Vulnerability Information
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Vulnerability Title
http4s-blaze-server: Unbounded WebSocket message aggregation
Source: CVE Program / CVE List V5
Vulnerability Description
Http4s (http4s-blaze-server) is a minimal, idiomatic Scala interface for HTTP services. Prior to 0.23.18 and 1.0.0-M42, http4s-blaze-server aggregates fragments of an incoming WebSocket message with no limit on total size or fragment count. A client that completes a WebSocket handshake can send an unterminated fragmented message and drive unbounded heap growth in the server JVM, resulting in denial of service through OutOfMemoryError. Any http4s application serving WebSocket routes over BlazeServerBuilder is affected, no non-default configuration is required, and maxWebSocketBufferSize does not bound the aggregate because it bounds only individual frames. A single connection sending continuation frames that never set FIN forces the server to buffer every fragment until the heap is exhausted, terminating the JVM with OutOfMemoryError on the blaze selector thread. Small fragments amplify the cost through per-frame object overhead, so a modest volume of wire bytes is sufficient. This issue is fixed in versions 0.23.18 and 1.0.0-M42.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
http4s blaze 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
http4s blaze是http4s组织的一款Web中间件组件。 http4s blaze 0.23.18之前版本和1.0.0-M42之前版本存在资源管理错误漏洞，该漏洞源于聚合WebSocket消息片段时未限制总大小或片段数量，可能导致服务器JVM堆无界增长，造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
http4s blaze < 0.23.18 -

II. Public POCs for CVE-2026-73493

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 8640 chars
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III. Intelligence Information for CVE-2026-73493

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Patches & Fixes for CVE-2026-73493 (1)

Vendor Advisories for CVE-2026-73493 (1)

Vendor Pages for CVE-2026-73493 (2)

IV. Related Vulnerabilities

Same product: blaze
Same vendor: http4s
Same weakness: CWE-770

V. Comments for CVE-2026-73493

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