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.

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:02739-2 advisory.

    - CVE-2025-6442: Fixed read_header HTTP Request Smuggling Vulnerability in WEBrick (bsc#1245254)
    - CVE-2025-27221: Fixed userinfo leakage in URI#join, URI#merge and URI#+ (bsc#1237805)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.04 host has a package installed that is affected by a vulnerability as referenced in the USN-7709-1 advisory.

    It was discovered that WEBrick incorrectly parsed HTTP headers. In configurations where WEBrick is placed     behind an HTTP proxy, a remote attacker could possibly use this issue to perform an HTTP Request Smuggling     attack.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2025-6442)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 / openSUSE 15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:02739-1 advisory.

    - CVE-2025-6442: Fixed read_header HTTP Request Smuggling Vulnerability in WEBrick (bsc#1245254)
    - CVE-2025-27221: Fixed userinfo leakage in URI#join, URI#merge and URI#+ (bsc#1237805)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It is, therefore, affected by a vulnerability as referenced in the ALAS2023-2025-1115 advisory.

    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. (CVE-2025-6442)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of ruby installed on the remote host is prior to 2.0.0.648-36. It is, therefore, affected by a vulnerability as referenced in the ALAS2-2025-2931 advisory.

    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. (CVE-2025-6442)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of ruby / rubygem-webrick installed on the remote CBL Mariner 2.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-6442 advisory.

  - 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. (CVE-2025-6442)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of ruby / rubygem-webrick installed on the remote Azure Linux 3.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-6442 advisory.

  - 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. (CVE-2025-6442)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of the WEBrick Ruby library installed on the remote host is prior to 1.8.2. It is, therefore, affected by an HTTP request smuggling vulnerability in the read_header. 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.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
260432	SUSE SLES15 Security Update : ruby2.5 (SUSE-SU-2025:02739-2)	Nessus	SuSE Local Security Checks	low
253653	Ubuntu 22.04 LTS / 24.04 LTS / 25.04 : WEBrick vulnerability (USN-7709-1)	Nessus	Ubuntu Local Security Checks	medium
251535	Linux Distros Unpatched Vulnerability : CVE-2025-6442	Nessus	Misc.	medium
246926	SUSE SLED15 / SLES15 / openSUSE 15 Security Update : ruby2.5 (SUSE-SU-2025:02739-1)	Nessus	SuSE Local Security Checks	low
243482	Amazon Linux 2023 : ruby3.2, ruby3.2-bundled-gems, ruby3.2-default-gems (ALAS2023-2025-1115)	Nessus	Amazon Linux Local Security Checks	medium
243248	Amazon Linux 2 : ruby (ALAS-2025-2931)	Nessus	Amazon Linux Local Security Checks	medium
241924	CBL Mariner 2.0 Security Update: ruby / rubygem-webrick (CVE-2025-6442)	Nessus	MarinerOS Local Security Checks	medium
241907	Azure Linux 3.0 Security Update: ruby / rubygem-webrick (CVE-2025-6442)	Nessus	Azure Linux Local Security Checks	medium
240854	Ruby WEBrick < 1.8.2 HTTP Request Smuggling	Nessus	Misc.	medium

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CVE-2025-6442

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