Vulnerability in Http4s
CVE-2025-59822
Http4s is a Scala interface for HTTP services. In versions from 1.0.0-M1 to before 1.0.0-M45 and before 0.23.31, http4s is vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section. This vulnerability could enable attackers to bypass front-end servers security controls, launch targeted attacks against active users, and poison web caches. A pre-requisite for exploitation involves the web application being deployed behind a reverse-proxy that forwards trailer headers. This issue has been patched in versions 1.0.0-M45 and 0.23.31.
Vulnerability class: HTTP Request Smuggling
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (28.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 28.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Http4s — versions < 0.23.31, >= 1.0.0-M1, < 1.0.0-M45
- Typelevel Http4s — versions 1.0.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/http4s/http4s/security/advisories/GHSA-wcwh-7gfw-5wrr (Exploit, Vendor Advisory)
- github.com/http4s/http4s/commit/dd518f7c967e5165813b8d4a48a82b8fab852d41 (Patch)
Frequently asked questions
- What is CVE-2025-59822?
- CVE-2025-59822 is a high-severity vulnerability in Http4s, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 7.5/10. Published 2025-09-23.
- How severe is CVE-2025-59822?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2025-59822 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.