What’s Vulnerable › Vulnerabilities

CVE-2026-69216: Http4s: Ember chunk parser lenience (TE.TE request smuggling)

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-15 · updated 2026-09-16
• Weakness: CWE-444

Description

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s chunk decoder trims the chunk-size token and accepts leading plus or minus signs instead of requiring one or more hexadecimal digits followed by the required CRLF. When an intermediary forwards chunked data without re-encoding and interprets malformed chunk boundaries differently, an unauthenticated attacker can create TE.TE request smuggling that bypasses intermediary controls, poisons caches, or hijacks the request queue. The same response-path leniency can enable response smuggling against an ember-client used as a gateway when the upstream is malicious or compromised. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Affected products

• http4s: before 0.23.35; from 1.0.0-M1, < 1.0.0-M47

References

• https://github.com/http4s/http4s/commit/d78612a5abd5a2547487598d3342be05573e16f0
• https://github.com/http4s/http4s/releases/tag/v0.23.35
• https://github.com/http4s/http4s/releases/tag/v1.0.0-M47
• https://github.com/http4s/http4s/security/advisories/GHSA-jrpm-956j-96jg

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