CVE-2026-69205

HIGH
Published Sep 15, 2026 Modified Sep 16, 2026 CWE-444

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.

Is your site exposed to CVE-2026-69205?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

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

EPSS — Exploit Prediction

0.0040
Probability of exploitation
0.33%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-444 CWE-444

References

Frequently Asked Questions

What is CVE-2026-69205? +
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. It has a CVSS v3.1 base score of 8.7 (HIGH).
How severe is CVE-2026-69205? +
CVE-2026-69205 has a CVSS v3.1 score of 8.7 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0040, placing it in the 0th percentile for exploitation probability.
How do I check if I'm vulnerable to CVE-2026-69205? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-63379

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked HTTP trailers in http.c through evhttp_read_trailer …
CVE-2025-1867

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows HTTP Response Smuggling.This issue affects libhv: through …
CVE-2024-23316

HTTP request desynchronization in Ping Identity PingAccess, all versions prior to 8.0.1 affected allows an attacker to send specially crafted …
CVE-2024-38494

This vulnerability allows a high-privileged authenticated PAM user to achieve remote command execution on the affected PAM system by sending …
CVE-2025-6999

An HTTP Request Smuggling [CWE-444] vulnerability in the Authentication portal of WatchGuard Fireware OS allows a remote attacker to evade …
CVE-2025-11915

Connection desynchronization between an HTTP proxy and the model backend. The fixes were rolled out for all proxies in front …

Don't wait for an exploit

Scan your website for vulnerabilities like CVE-2026-69205 — free, no signup required.