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CVE-2026-73493 high CVSS 7.5

Vulnerability in org.http4s:http4s-blaze-server_2.13 (CVE-2026-73493)

Summary

Vulnerability in org.http4s:http4s-blaze-server_2.13 (CVE-2026-73493). Risk of unauthorized operations or information disclosure. Exploitable via OutOfMemoryError. Mitigation: upgrade to 1.0.0-M42 or later.

Original description

The description as published by the source.

Summary

http4s-blaze-server aggregates the 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 via OutOfMemoryError.

Impact

Any http4s application serving WebSocket routes over
BlazeServerBuilder is affected; no non-default configuration is required,
and maxWebSocketBufferSize does not bound the aggregate (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. Where the
WebSocket endpoint is reachable without authentication the attacker is
unauthenticated and remote; where the handshake requires a principal, any
authenticated client can still trigger it.

Workarounds

  • No blaze-server configuration bounds the aggregate; maxWebSocketBufferSize
    is not a mitigation.
  • Terminate/limit WebSocket traffic at a fronting layer that enforces
    message-size and fragment limits, or disable WebSocket routes.
  • Longer term: blaze is EOL upstream; plan migration to a maintained
    backend (e.g. ember).

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-73493 has been found in org.http4s:http4s-blaze-server_2.13.
Attackers can target a specific entry point like OutOfMemoryError over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade org.http4s:http4s-blaze-server_2.13 to 1.0.0-M42 or later.
If unsure, ask your IT team or search "org.http4s:http4s-blaze-server_2.13 CVE-2026-73493" on the vendor's site.

CVE-2026-73493 (org.http4s:http4s-blaze-server_2.13) — CWE-770 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: OutOfMemoryError / BlazeServerBuilder / maxWebSocketBufferSize
Patched: 1.0.0-M42 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-770) exists in org.http4s:http4s-blaze-server_2.13. Attackers reach the vulnerable code path via OutOfMemoryError without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of org.http4s:http4s-blaze-server_2.13. Attack surface: OutOfMemoryError / BlazeServerBuilder / maxWebSocketBufferSize.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.0.0-M42.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで org.http4s:http4s-blaze-server_2.13 を使っているサービスとバージョンを洗い出す。

  2. 2
    Apply patch patch 
    Upgrade org.http4s:http4s-blaze-server_2.13 to 1.0.0-M42

    ステージング環境で 1.0.0-M42 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

maven org.http4s:http4s-blaze-server_2.13
[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.0-M1"},{"fixed":"1.0.0-M42"}]}]
maven org.http4s:http4s-blaze-server_2.12
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.23.18"}]}]
maven org.http4s:http4s-blaze-server_3
[{"type":"ECOSYSTEM","events":[{"introduced":"1.0.0-M1"},{"fixed":"1.0.0-M42"}]}]

References

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