Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary that forwards both headers and frames by Content-Length, an unauthenticated attacker can smuggle a second request, bypass intermediary access controls, poison caches, or cause a victim request to be joined to an attacker-controlled prefix. The shared response parser can also desynchronize an ember-client connection when a malicious or compromised upstream sends both headers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
CVE-2026-69204
CRITICALPre-NVD 9.29.2—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This critical-severity CVE scores 9.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 74% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.2EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.2Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.2
- EG Score
- 9.2(medium)
- EG Risk
- 42(Track)EG Risk 42/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity92% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 26%
- KEV
- Not listed
Published
September 15, 2026
Last Modified
September 16, 2026
Advisory Details (4)
Auto-updated Sep 15, 2026Patch available. Sources: github_commit, github_release, github.
github Patch Available
Ember accepts Transfer-Encoding combined with Content-Length (CL.TE request smuggling) · Advisory · http4s/http4s · GitHub
https://github.com/http4s/http4s/security/advisories/GHSA-8h4c-x2wg-6xp8github_release Patch Available
v1.0.0-M47
Patch available: http4s/http4s v1.0.0-M47 (pre-release)
https://github.com/http4s/http4s/releases/tag/v1.0.0-M47github_release Patch Available
v0.23.35
Patch available: http4s/http4s v0.23.35
https://github.com/http4s/http4s/releases/tag/v0.23.35github_commit Patch Available
commit 9feaf8677951 (http4s/http4s)
Patch available: http4s/http4s v0.23.35 (contains commit 9feaf8677951)
https://github.com/http4s/http4s/commit/9feaf8677951a52af906ae9664ff6f0543d9d810Vendor Advisories for CVE-2026-69204(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(3 across 1 ecosystem)
Maven(3)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| org.http4s:http4s-ember-core_2.12 | 0.10.0-M10 ... 0.23.9 (114 versions) | 0.23.35 | — |
| org.http4s:http4s-ember-core_2.13 | 0.10.0-M10 ... 0.23.9 (114 versions) | 0.23.35 | — |
| org.http4s:http4s-ember-core_3 | 0.22.0 ... 0.23.9 (58 versions) | 0.23.35 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 9× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-09-18 22:02 UTCEG score recompute
- 2026-09-18 19:28 UTCEPSS rescore
- 2026-09-17 22:35 UTCEG score recompute
- 2026-09-16 15:02 UTCEG score recompute
- 2026-09-16 14:08 UTCEPSS rescore
- 2026-09-15 19:34 UTCEG score recompute
- 2026-09-15 19:13 UTCEG score recompute
- 2026-09-15 18:48 UTCEG score recompute
- 2026-09-15 18:47 UTCMITRE cvelistV5first tracked
Frequently asked(5)
What is CVE-2026-69204?
CVE-2026-69204 is a critical vulnerability published on September 15, 2026. Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary…
When was CVE-2026-69204 disclosed?
CVE-2026-69204 was first published in the National Vulnerability Database on September 15, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-69204 actively exploited?
CVE-2026-69204 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.6% of all scored CVEs.
What is the CVSS score of CVE-2026-69204?
CVE-2026-69204 has a CVSS v3 base score of 9.2 (NVD).
How do I remediate CVE-2026-69204?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-69204, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-69204
Is Your Infrastructure Affected by CVE-2026-69204?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.