Vulnerability in org.http4s:http4s-ember-core_2.12 (CVE-2026-54556)
Summary
Vulnerability in org.http4s:http4s-ember-core_2.12 (CVE-2026-54556). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 0.23.35 or later.
Original description
The description as published by the source.
Summary
http4s 0.23.x and 1.0 servers running ember with http2 enabled are vulnerable to a denial of service attack using a HPACK bomb vulnerability recently disclosed as affecting other http2 servers.
Impact
Denial of Service:
- Affects any http4s server running the ember backend with HTTP/2 enabled that is exposed to untrusted traffic.
- Affects any http4s client running the ember backend with HTTP/2 enabled that can be directed to an untrusted server.
Details
The issue occurs in the Hpack wrapper. Ember concatenates the header and continuation frames before decoding all headers at once. When the code decodes the attack payload, the relatively small packets decode to a significantly larger amount of data which is returned as a single List which is then held in memory for further processing. With enough concurrent connections (~5 with a 2GB heap in testing) this leads to an OOM, eg:
java.lang.OutOfMemoryError: Java heap space
at scala.collection.mutable.ListBuffer.scala$collection$mutable$ListBuffer$$freshFrom(ListBuffer.scala:129)
at scala.collection.mutable.ListBuffer.addAll(ListBuffer.scala:147)
at scala.collection.mutable.ListBuffer.addAll(ListBuffer.scala:40)
at scala.collection.mutable.Growable.$plus$plus$eq(Growable.scala:69)
at scala.collection.mutable.…
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-2026-54556 has been found in org.http4s:http4s-ember-core_2.12.
Risk of unauthorized operations or information disclosure.
What to do: upgrade org.http4s:http4s-ember-core_2.12 to 0.23.35 or later.
If unsure, ask your IT team or search "org.http4s:http4s-ember-core_2.12 CVE-2026-54556" on the vendor's site.
CVE-2026-54556 (org.http4s:http4s-ember-core_2.12) — CWE-409
Patched: 0.23.35 — 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.
A vulnerability (CWE-409) exists in org.http4s:http4s-ember-core_2.12.
Check the vendor advisory for the affected versions of org.http4s:http4s-ember-core_2.12.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 0.23.35.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
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
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1Identify 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-ember-core_2.12 を使っているサービスとバージョンを洗い出す。
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2Apply patch patch
Upgrade org.http4s:http4s-ember-core_2.12 to 0.23.35ステージング環境で 0.23.35 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。
-
3Post-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
References
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com