Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M
CVE-2026-69205Http4s: Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)
High 8.7
In plain English
A high-severity security flaw in http4s from http4s. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HeaderP.parse uses a case-sensitive substring test for the Transfer-Encoding value and decodes header bytes with the platform default charset. Values such as Chunked are not recognized, values such as notchunked are incorrectly accepted, and Unicode case folding can turn a Kelvin-sign byte sequence into a match when UTF-8 is used. Intermediaries that apply RFC-compliant token and charset rules can therefore disagree with Ember’s Content-Length or zero-length framing, enabling TE.CL or TE.0 request smuggling, access-control bypass, cross-user request hijacking, and cache poisoning on the server path. Response smuggling through an ember-client gateway requires a malicious or compromised upstream. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Maven | org.http4s:http4s-ember-core_2.12 | 0.23.35 | GHSA-9998-894r-fwvr |
| Maven | org.http4s:http4s-ember-core_2.13 | 0.23.35 | GHSA-9998-894r-fwvr |
| Maven | org.http4s:http4s-ember-core_2.13 | 1.0.0-M47 | GHSA-9998-894r-fwvr |
| Maven | org.http4s:http4s-ember-core_3 | 0.23.35 | GHSA-9998-894r-fwvr |
| Maven | org.http4s:http4s-ember-core_3 | 1.0.0-M47 | GHSA-9998-894r-fwvr |
Affected products (as reported)
Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
References
- https://github.com/http4s/http4s/security/advisories/GHSA-9998-894r-fwvr x_refsource_CONFIRM
- https://github.com/http4s/http4s/commit/5e88b2e7b4e6ea2f0c61040a4bc9de0d73e51217 x_refsource_MISC
- https://github.com/http4s/http4s/releases/tag/v0.23.35 x_refsource_MISC
- https://github.com/http4s/http4s/releases/tag/v1.0.0-M47 x_refsource_MISC