High severity · published Sep 23, 2025
CVE-2025-59822
Http4s vulnerable to HTTP Request Smuggling due to improper handling of HTTP trailer section
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HT
http4s · http4s
< 0.23.31; >= 1.0.0-M1, < 1.0.0-M45 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-59822
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-59822
Patch
https://github.com/http4s/http4s/commit/dd518f7c967e5165813b8d4a48a82b8fab852d41
Exploit
https://github.com/http4s/http4s/security/advisories/GHSA-wcwh-7gfw-5wrr
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