Http4s Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-69205: 0.48% estimated exploitation activity in the next 30 days; percentile 41.45 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Ember's HTTP/1.1 header parser matches the Transfer-Encoding header value with a case-sensitive substring test (hValue.contains("chunked")). RFC 9112 §7 requires transfer-coding names to be compared case-insensitively. A request carrying Transfer-Encoding: Chunked (capital C) is therefore not recognised as chunked, and Ember falls back to framing by Content-Length (or zero if absent) while a compliant intermediary frames the same bytes by chunked encoding. The two parsers then disagree on where the request body ends, enabling HTTP request smuggling (TE.CL / TE.0). The same line of code admits two further variants: - The substring test misfires on Transfer-Encoding: notchunked (an inverse desync — Ember treats it as chunked while a compliant intermediary rejects the unknown coding). - Header field bytes are decoded with the platform-default charset. Under UTF-8 the wire bytes E2 84 AA decode to U+212A KELVIN SIGN, which String.equalsIgnoreCase Unicode-case-folds to k, so…

Published by the source

15 Sep 2026, 19:54 UTC

Last modified by the source

15 Sep 2026, 20:00 UTC

Source last checked

26 Oct 2026, 16:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9998-894r-fwvr

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9998-894r-fwvr

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-69205

Advisory: Http4s Ember Transfer-Encoding value parsing (TE.CL / TE.0 request smuggling)
IDs: CVE-2026-69205, GHSA-9998-894r-fwvr
Record: https://patchnext.com/advisories/cve-2026-69205 (revision 2, source checked 26 Oct 2026, 16:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.http4s:http4s-ember-core_2.12 0.23.35; org.http4s:http4s-ember-core_3 1.0.0-M47, 0.23.35; org.http4s:http4s-ember-core_2.13 1.0.0-M47, 0.23.35. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.http4s:http4s-ember-core_2.12: affected <= 0.23.34; fixed in 0.23.35
- Maven org.http4s:http4s-ember-core_3: affected <= 0.23.34; >= 1.0.0-M1, <= 1.0.0-M46; fixed in 0.23.35, 1.0.0-M47
- Maven org.http4s:http4s-ember-core_2.13: affected <= 0.23.34; >= 1.0.0-M1, <= 1.0.0-M46; fixed in 0.23.35, 1.0.0-M47

## Suggested inspection (read-only)
- Maven org.http4s:http4s-ember-core_2.12: check the installed version with your package manager.
- Maven org.http4s:http4s-ember-core_3: check the installed version with your package manager.
- Maven org.http4s:http4s-ember-core_2.13: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.http4s:http4s-ember-core_2.12, org.http4s:http4s-ember-core_3, org.http4s:http4s-ember-core_2.13.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9998-894r-fwvr (OSV record GHSA-9998-894r-fwvr lists affected ranges: Maven org.http4s:http4s-ember-core_3 >=0 =1.0.0-M1 =0 =1.0.0-M1 =0 <0.23.35 (fixed))
- Verified: https://github.com/advisories/GHSA-9998-894r-fwvr (GitHub-reviewed advisory GHSA-9998-894r-fwvr lists affected ranges: Maven org.http4s:http4s-ember-core_3 >=0 =1.0.0-M1 =0 =1.0.0-M1 =0 <=0.23.34)

Commands are suggestions: review each one before running it.