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Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M

CVE-2026-69218Http4s Ember HTTP/2: unbounded continuation frame accumulation

High 7.5

In plain English

A high-severity resource allocation without limits in http4s from http4s. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.6%top 49.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, When Ember receives an HTTP/2 HEADERS or PUSH_PROMISE frame without END_HEADERS, H2Connection buffers the header block and subsequent CONTINUATION fragments without a size bound. A remote peer can keep an incomplete block open and exhaust heap memory before request decoding, affecting an ember-server or ember-client configured with withHttp2. The remediation tracks accumulated size against SETTINGS_MAX_HEADER_LIST_SIZE derived from EmberServerBuilder.maxHeaderSize or EmberClientBuilder.maxResponseHeaderSize, sends GOAWAY when the limit is exceeded, and applies receiveHeadersTimeout to incomplete blocks. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Mavenorg.http4s:http4s-ember-core_2.120.23.35GHSA-cp4q-fqw9-4hf6
Mavenorg.http4s:http4s-ember-core_2.130.23.35GHSA-cp4q-fqw9-4hf6
Mavenorg.http4s:http4s-ember-core_2.131.0.0-M47GHSA-cp4q-fqw9-4hf6
Mavenorg.http4s:http4s-ember-core_30.23.35GHSA-cp4q-fqw9-4hf6
Mavenorg.http4s:http4s-ember-core_31.0.0-M47GHSA-cp4q-fqw9-4hf6

Affected products (as reported)

VendorProductVersions
http4s http4s < 0.23.35>= 1.0.0-M1, < 1.0.0-M47

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References