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

Q: How do I fix CVE-2025-6442?

webrick: upgrade to 1.8.2. Exact commands for each OS are on this page.

Q: Is CVE-2025-6442 being exploited?

CVE-2025-6442 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2025-6442 affect?

CVE-2025-6442 affects webrick. Severity is medium (CVSS 5.9). 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 b

Q: How urgent is CVE-2025-6442?

Priority 36/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 5.9REMOTEUPGRADE

CVE-2025-6442 is a medium-severity flaw (CVSS 5.9) affecting webrick. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 l

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-444
Published	2025-06-25
Last modified	2026-06-17

Publisher (CNA): Zero Day Initiative · Vendor: ruby-lang

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-06-25 17:15 UTCPublished CVE record published
2026-06-17 10:01 UTCUpdated Record last modified

ruby-lang webrick UPGRADE

Affected: < 1.8.2

Fixed in: 1.8.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy webrick || rpm -q webrick || webrick --version

2. UPGRADE to 1.8.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade webrick

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade webrick

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-6442?

webrick: upgrade to 1.8.2. Exact commands for each OS are on this page.

Is CVE-2025-6442 being exploited?

CVE-2025-6442 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-6442 affect?

CVE-2025-6442 affects webrick. Severity is medium (CVSS 5.9). 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 b

How urgent is CVE-2025-6442?

Priority 36/100. Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

References

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