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Medium, CVSS 6.5

Ruby WEBrick read_headers method can lead to HTTP Request/Response Smuggling

CVE-2025-6442GHSA-r995-q44h-hr64

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (webrick 1.8.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • RubyGems webrick

    Affected
    < 1.8.2
    Fixed in
    1.8.2

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.5 · CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
EPSS
  • CVE-2025-6442: 0.50% estimated exploitation activity in the next 30 days; percentile 42.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Ruby WEBrick readheader 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 readheaders 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.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-r995-q44h-hr64

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-6442

Advisory: Ruby WEBrick read_headers method can lead to HTTP Request/Response Smuggling
IDs: CVE-2025-6442, GHSA-r995-q44h-hr64
Record: https://patchnext.com/advisories/cve-2025-6442 (revision 1, source checked 26 Oct 2026, 15:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: webrick 1.8.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems webrick: affected < 1.8.2; fixed in 1.8.2

## Suggested inspection (read-only)
- RubyGems webrick: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on webrick.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-r995-q44h-hr64 (GitHub-reviewed advisory GHSA-r995-q44h-hr64 lists affected ranges: RubyGems webrick >=0 <1.8.2)

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