Http4s Ember HTTP/2: unbounded inbound body buffering

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-69202: 0.63% estimated exploitation activity in the next 30 days; percentile 50.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Ember's HTTP/2 stack replenishes the inbound flow-control window based on bytes received off the wire, not bytes consumed by the application. Received DATA is buffered in an unbounded per-stream channel. Flow control therefore provides no backpressure: a peer can stream a large or unbounded body faster than the application drains it and the connection retains every payload in heap. This is the read-path mirror of the outbound queue issue. This affects an Ember receiving a request body and an Ember client receiving a response body from a hostile server. Impact Unauthenticated remote denial of service (OOM) against any Ember server built .withHttp2 for a non-draining or slow-draining route, and against an Ember client consuming from a hostile or compromised server. Workarounds - Disable HTTP/2 to remove the vector entirely. - Apply an aggregate request-entity size limit (e.g. EntityLimiter middleware) on routes that consume the body. - Ensure handlers fully drain request bodies with…

Published by the source

15 Sep 2026, 19:52 UTC

Last modified by the source

15 Sep 2026, 20:00 UTC

Source last checked

26 Oct 2026, 16:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-6m4x-pp6q-5jmm

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-6m4x-pp6q-5jmm

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# Patch Next advisory brief: CVE-2026-69202

Advisory: Http4s Ember HTTP/2: unbounded inbound body buffering
IDs: CVE-2026-69202, GHSA-6m4x-pp6q-5jmm
Record: https://patchnext.com/advisories/cve-2026-69202 (revision 2, source checked 26 Oct 2026, 16:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.http4s:http4s-ember-core_2.12 0.23.35; org.http4s:http4s-ember-core_3 1.0.0-M47, 0.23.35; org.http4s:http4s-ember-core_2.13 1.0.0-M47, 0.23.35. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.http4s:http4s-ember-core_2.12: affected <= 0.23.34; fixed in 0.23.35
- Maven org.http4s:http4s-ember-core_3: affected <= 0.23.34; >= 1.0.0-M1, <= 1.0.0-M46; fixed in 0.23.35, 1.0.0-M47
- Maven org.http4s:http4s-ember-core_2.13: affected <= 0.23.34; >= 1.0.0-M1, <= 1.0.0-M46; fixed in 0.23.35, 1.0.0-M47

## Suggested inspection (read-only)
- Maven org.http4s:http4s-ember-core_2.12: check the installed version with your package manager.
- Maven org.http4s:http4s-ember-core_3: check the installed version with your package manager.
- Maven org.http4s:http4s-ember-core_2.13: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.http4s:http4s-ember-core_2.12, org.http4s:http4s-ember-core_3, org.http4s:http4s-ember-core_2.13.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-6m4x-pp6q-5jmm (OSV record GHSA-6m4x-pp6q-5jmm lists affected ranges: Maven org.http4s:http4s-ember-core_2.12 >=0 =0 =1.0.0-M1 =0 =1.0.0-M1 <1.0.0-M47 (fixed))
- Verified: https://github.com/advisories/GHSA-6m4x-pp6q-5jmm (GitHub-reviewed advisory GHSA-6m4x-pp6q-5jmm lists affected ranges: Maven org.http4s:http4s-ember-core_2.12 >=0 =0 =1.0.0-M1 =0 =1.0.0-M1 <=1.0.0-M46)

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