CVE-2025-6442 | Ruby WEBrick read_header HTTP Request Smuggling Vulnerability

Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-CAN-21876.

Published: 2025-06-25 Last update: 2025-08-18 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-6442 is rated Moderate Risk (41/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.26%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-6442

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-21 0.06% 0.26% +0.20%
2 2026-01-19 0.04% 0.06% +0.02%
3 2025-11-21 — 0.04% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-6442

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 3.6 [email protected]
6.5 3.0 MEDIUM
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 4.2 [email protected]

Weakness enumeration for CVE-2025-6442

GitHub Security Advisory for CVE-2025-6442

GHSA-r995-q44h-hr64 · Severity: medium · Ecosystem: rubygems — Ruby WEBrick read_headers method can lead to HTTP Request/Response Smuggling

OS Trackers for CVE-2025-6442

vendor priority summary link
alpine — CVE-2025-6442: 1 source package rows (ruby-webrick); 2 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 2. https://security.alpinelinux.org/vuln/CVE-2025-6442
debian not yet assigned CVE-2025-6442 not yet assigned priority: Debian including 1 source packages (ruby-webrick), 4 status rows across 4 suites (bookworm, forky, sid, trixie): resolved 3, open 1. https://security-tracker.debian.org/tracker/CVE-2025-6442
redhat medium — https://access.redhat.com/security/cve/CVE-2025-6442
suse medium — https://www.suse.com/security/cve/CVE-2025-6442/
ubuntu medium CVE-2025-6442 medium priority: Ubuntu including 5 source packages (jruby, ruby-webrick, ruby2.3, ruby2.5, ruby2.7), 33 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 13, released 8, needed 4, needs-triage 4, not-affected 3, ignored 1. https://ubuntu.com/security/CVE-2025-6442

Affected software / configurations for CVE-2025-6442

Vendor Product Version Raw CPE
ruby-lang webrick < 1.8.2 cpe:2.3:a:ruby-lang:webrick:*:*:*:*:*:ruby:*:*

References for CVE-2025-6442

cvelogic Threat Intelligence