CVE-2026-88975
Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGS_MAX_FRAME_SIZE. An unauthenticated peer can declare a payload near 16 MiB on a connection where Ember advertised 16 KiB and either complete or slowly stream it, causing up to 1024-fold memory amplification per connection before processFrame can reject the frame. The shared H2Connection.readLoop affects withHttp2 servers and clients, while HTTP/2-disabled configurations are unaffected, and the patch rejects oversized frames before buffering their payloads. This issue is fixed in versions 0.23.37 and 1.0.0-M48.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Deferred | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.63% · top 50% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Mavenorg.http4s:http4s-ember-core_2.12GHSA-gq9p-f254-h286 (opens in a new tab)
- Mavenorg.http4s:http4s-ember-core_2.13GHSA-gq9p-f254-h286 (opens in a new tab)
- Mavenorg.http4s:http4s-ember-core_3GHSA-gq9p-f254-h286 (opens in a new tab)
References (4)
- https://github.com/http4s/http4s/security/advisories/GHSA-gq9p-f254-h286 (opens in a new tab)x_refsource_CONFIRM
- https://github.com/http4s/http4s/commit/87cf334fa3f608ef7d3eb359e71e037ba3336d29 (opens in a new tab)x_refsource_MISC
- https://github.com/http4s/http4s/releases/tag/v0.23.37 (opens in a new tab)x_refsource_MISC
- https://github.com/http4s/http4s/releases/tag/v1.0.0-M48 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-gq9p-f254-h286 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-88975)Record last updated .