Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Starting in version 0.3.2 and prior to versions 0.3.8, 0.4.19, and 0.5.6, there is a possibility for denial of service by memory exhaustion in `net-imap`'s response parser. At any time while the client is connected, a malicious server can send can send highly compressed `uid-set` data which is automatically read by the client's receiver thread. The response parser uses `Range#to_a` to convert the `uid-set` data into arrays of integers, with no limitation on the expanded size of the ranges. Versions 0.3.8, 0.4.19, 0.5.6, and higher fix this issue. Additional details for proper configuration of fixed versions and backward compatibility are available in the GitHub Security Advisory.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2025-929 advisory.

    Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Starting in     version 0.3.2 and prior to versions 0.3.8, 0.4.19, and 0.5.6, there is a possibility for denial of service     by memory exhaustion in `net-imap`'s response parser.  At any time while the client is connected, a     malicious server can send  can send highly compressed `uid-set` data which is automatically read by the     client's receiver thread. The response parser uses `Range#to_a` to convert the `uid-set` data into arrays     of integers, with no limitation on the expanded size of the ranges. Versions 0.3.8, 0.4.19, 0.5.6, and     higher fix this issue. Additional details for proper configuration of fixed versions and backward     compatibility are available in the GitHub Security Advisory. (CVE-2025-25186)

    In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential     Denial of Service (DoS) vulnerability. The method does not impose any limit on the length of the raw     cookie value it processes. This oversight can lead to excessive resource consumption when parsing     extremely large cookies. (CVE-2025-27219)

    In the CGI gem before 0.4.2 for Ruby, a Regular Expression Denial of Service (ReDoS) vulnerability exists     in the Util#escapeElement method. (CVE-2025-27220)

Tenable has extracted the preceding description block directly from the tested product 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 20.04 LTS / 22.04 LTS / 24.04 LTS / 24.10 host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-7418-1 advisory.

    It was discovered that Ruby incorrectly handled parsing of an XML document that has specific XML     characters in an attribute value using REXML gem. An attacker could use this issue to cause Ruby to crash,     resulting in a denial of service. This issue only affected in Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and     Ubuntu 24.10. (CVE-2024-35176, CVE-2024-39908, CVE-2024-41123, CVE-2024-43398)

    It was discovered that Ruby incorrectly handled expanding ranges in the net-imap response parser. If a     user or automated system were tricked into connecting to a malicious IMAP server, a remote attacker could     possibly use this issue to consume memory, leading to a denial of service. This issue only affected Ubuntu     24.04 LTS, and Ubuntu 24.10. (CVE-2025-25186)

    It was discovered that the Ruby CGI gem incorrectly handled parsing certain cookies. A remote attacker     could possibly use this issue to consume resources, leading to a denial of service. (CVE-2025-27219)

    It was discovered that the Ruby CGI gem incorrectly handled parsing certain regular expressions. A remote     attacker could possibly use this issue to consume resources, leading to a denial of service.
    (CVE-2025-27220)

    It was discovered that the Ruby URI gem incorrectly handled certain URI handling methods. A remote     attacker could possibly use this issue to leak authentication credentials. (CVE-2025-27221)

Tenable has extracted the preceding description block directly from the Ubuntu 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 Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Starting in     version 0.3.2 and prior to versions 0.3.8, 0.4.19, and 0.5.6, there is a possibility for denial of service     by memory exhaustion in `net-imap`'s response parser. At any time while the client is connected, a     malicious server can send can send highly compressed `uid-set` data which is automatically read by the     client's receiver thread. The response parser uses `Range#to_a` to convert the `uid-set` data into arrays     of integers, with no limitation on the expanded size of the ranges. Versions 0.3.8, 0.4.19, 0.5.6, and     higher fix this issue. Additional details for proper configuration of fixed versions and backward     compatibility are available in the GitHub Security Advisory. (CVE-2025-25186)

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

ID	Name	Product	Family	Severity
234332	Amazon Linux 2023 : ruby3.2, ruby3.2-bundled-gems, ruby3.2-default-gems (ALAS2023-2025-929)	Nessus	Amazon Linux Local Security Checks	medium
233968	Ubuntu 20.04 LTS / 22.04 LTS / 24.04 LTS / 24.10 : Ruby vulnerabilities (USN-7418-1)	Nessus	Ubuntu Local Security Checks	medium
231296	Linux Distros Unpatched Vulnerability : CVE-2025-25186	Nessus	Misc.	medium

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