High 7.5Published Sep 15, 2026

CVE-2026-69213Http4s Ember HTTP/2: unbounded outbound frame queue

Updated under an hour ago (2026-10-19 08:00 UTC)

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Exploited in the last 30 days

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can continue sending PING, SETTINGS, or DATA frames that cause Ember to enqueue acknowledgments or WINDOW_UPDATE frames faster than the writer drains them, exhausting heap memory on a server built with withHttp2. The shared behavior also affects an ember-client connected to a hostile HTTP/2 server, and the patch replaces the unbounded path with bounded, backpressured outbound queues. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-400, CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Sep 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

http4s http4s http4s:http4s (from the name)	before 0.23.35; from 1.0.0-M1, < 1.0.0-M47	CNA record

References

https://github.com/http4s/http4s/security/advisories/GHSA-8f3q-3jmv-7prwx-refsource-confirm
https://github.com/http4s/http4s/commit/13fe24d6440bde2f1eb70121486cf59c278e6baex-refsource-misc
https://github.com/http4s/http4s/releases/tag/v0.23.35x-refsource-misc
https://github.com/http4s/http4s/releases/tag/v1.0.0-M47x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.