Answer in brief
CVE-2026-88975 records a High severity (CVSS 7.5) vulnerability in Http4s: Ember HTTP/2 buffers a frame's declared payload before checking SETTINGS_MAX_FRAME_SIZE. The current sources do not mark it as known exploited. The current feed maps http4s/http4s (generic), org.http4s:http4s-ember-core_2.12 (maven), org.http4s:http4s-ember-core_2.13 (maven), org.http4s:http4s-ember-core_2.13 (maven) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps http4s/http4s (generic), org.http4s:http4s-ember-core_2.12 (maven), org.http4s:http4s-ember-core_2.13 (maven), org.http4s:http4s-ember-core_2.13 (maven) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| http4s/http4sgeneric | < 0.23.37 || >= 1.0.0-M1, < 1.0.0-M48 | Not reported |
| org.http4s:http4s-ember-core_2.12maven | <=0.23.36 | 0.23.37 |
| org.http4s:http4s-ember-core_2.13maven | <=0.23.36 | 0.23.37 |
| org.http4s:http4s-ember-core_2.13maven | >=1.0.0-M1,<=1.0.0-M47 | 1.0.0-M48 |
| org.http4s:http4s-ember-core_3maven | <=0.23.36 | 0.23.37 |
| org.http4s:http4s-ember-core_3maven | >=1.0.0-M1,<=1.0.0-M47 | 1.0.0-M48 |
Published upstream
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 15, 2026
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.
Quoted source text, attributed separately from HOL analysis.