# CVE-2026-88975

## Summary

- **CVE ID:** CVE-2026-88975
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-400
- **Published:** Sep 15, 2026
- **Last Modified:** Sep 16, 2026

## 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.

## Affected Products

- http4s — http4s (< 0.23.37)
- http4s — http4s (>= 1.0.0-M1, < 1.0.0-M48)

## References

- [CNA](https://github.com/http4s/http4s/security/advisories/GHSA-gq9p-f254-h286)
- [CNA](https://github.com/http4s/http4s/commit/87cf334fa3f608ef7d3eb359e71e037ba3336d29)
- [CNA](https://github.com/http4s/http4s/releases/tag/v0.23.37)
- [CNA](https://github.com/http4s/http4s/releases/tag/v1.0.0-M48)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.62%
- **EPSS Percentile:** 48.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._