CVE-2026-47240 - Medium Severity Vulnerability
Vulnerable Library - net-imap-0.6.4.gem
Ruby client api for Internet Message Access Protocol
Library home page: https://rubygems.org/gems/net-imap-0.6.4.gem
Path to dependency file: /Gemfile.lock
Path to vulnerable library: /tmp/containerbase/cache/.ruby/cache/net-imap-0.6.4.gem
Dependency Hierarchy:
- rails-8.0.5.gem (Root Library)
- actionmailer-8.0.5.gem
- mail-2.9.0.gem
- ❌ net-imap-0.6.4.gem (Vulnerable Library)
Found in base branch: master
Vulnerability Details
Several Net::IMAP commands accept a "raw data" argument that is sent verbatim after validation to prevent command injection. However, if a server does not support non-synchronizing literals, it may still be possible to inject arbitrary IMAP commands inside non-synchronizing literals. Details Raw data arguments support embedded literal values, both synchronizing and non-synchronizing. Non-synchronizing literals can only be safely sent when the server advertises any of the "LITERAL+", "LITERAL-", or "IMAP4rev2" capabilities. But raw data arguments do not verify server support for non-synchronizing literals prior to sending. Servers without support for non-synchronizing literals could handle them in several different ways: If a server sees a ""}\r\n"" byte sequence but can't parse the literal bytesize, it may cautiously decide to close the connection, blocking any command injection attacks. However, a server without support for non-synchronizing literals may instead interpret the ""+}\r\n"" as the end of a malformed command line and respond with a tagged "BAD". In that case, the contents of the literal will be interpreted as one or more new pipelined commands, allowing a CRLF command injection attack to succeed. This affects the following commands' string arguments: * "criteria" for "#search" and "#uid_search" * "search_keys" for "#sort", "#thread", "#uid_sort", and "#uid_thread" * "attr" for "#fetch" and "#uid_fetch" Prior to "net-imap" v0.6.4, v0.5.14, and v0.4.24, raw data arguments were not validated in any way, so they were also vulnerable to this attack. See CVE-2026-42257 (GHSA-hm49-wcqc-g2xg). Impact Fortunately, "LITERAL-" is supported by most modern IMAP servers. Even without support for non-synchronizing literals, cautious servers may handle invalid literal bytesize by closing the connection . However, servers which handle a non-synchronizing literal just like any other malformed command will enable this vulnerability. If a developer passes an unvalidated user-controlled input for one of these method arguments, an attacker can append CRLF sequence followed by a new IMAP command (like DELETE mailbox). Although this does not directly enable data exfiltration, it could be combined with other attack vectors or knowledge of the target system's attributes, e.g.: shared mail folders or the application's installed response handlers. Mitigation Update to a version of "net-imap" which validates server support for non-synchronizing literals before sending them. If upgrading "net-imap" is not possible: * Explicitly validate user-controlled inputs to prevent embedded non-synchronizing literals unless the server supports them. * For a simpler, more cautious approach: all embedded literals can be unconditionally prohibited, by checking that string inputs do not contain any CR or LF bytes. * Verify that the server advertises any of the "LITERAL+", "LITERAL-", or "IMAP4rev2" capabilities before using untrusted string inputs for the affected "raw data" arguments.
Publish Date: 2026-06-11
URL: CVE-2026-47240
CVSS 3 Score Details (6.1)
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Local
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: Required
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: High
- Availability Impact: Low
For more information on CVSS3 Scores, click here.
Suggested Fix
Type: Upgrade version
Release Date: 2026-06-11
Fix Resolution: https://github.com/ruby/net-imap.git - 0.5.15,net-imap - 0.6.4.1,net-imap - 0.5.15
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CVE-2026-47240 - Medium Severity Vulnerability
Ruby client api for Internet Message Access Protocol
Library home page: https://rubygems.org/gems/net-imap-0.6.4.gem
Path to dependency file: /Gemfile.lock
Path to vulnerable library: /tmp/containerbase/cache/.ruby/cache/net-imap-0.6.4.gem
Dependency Hierarchy:
Found in base branch: master
Several Net::IMAP commands accept a "raw data" argument that is sent verbatim after validation to prevent command injection. However, if a server does not support non-synchronizing literals, it may still be possible to inject arbitrary IMAP commands inside non-synchronizing literals. Details Raw data arguments support embedded literal values, both synchronizing and non-synchronizing. Non-synchronizing literals can only be safely sent when the server advertises any of the "LITERAL+", "LITERAL-", or "IMAP4rev2" capabilities. But raw data arguments do not verify server support for non-synchronizing literals prior to sending. Servers without support for non-synchronizing literals could handle them in several different ways: If a server sees a ""}\r\n"" byte sequence but can't parse the literal bytesize, it may cautiously decide to close the connection, blocking any command injection attacks. However, a server without support for non-synchronizing literals may instead interpret the ""+}\r\n"" as the end of a malformed command line and respond with a tagged "BAD". In that case, the contents of the literal will be interpreted as one or more new pipelined commands, allowing a CRLF command injection attack to succeed. This affects the following commands' string arguments: * "criteria" for "#search" and "#uid_search" * "search_keys" for "#sort", "#thread", "#uid_sort", and "#uid_thread" * "attr" for "#fetch" and "#uid_fetch" Prior to "net-imap" v0.6.4, v0.5.14, and v0.4.24, raw data arguments were not validated in any way, so they were also vulnerable to this attack. See CVE-2026-42257 (GHSA-hm49-wcqc-g2xg). Impact Fortunately, "LITERAL-" is supported by most modern IMAP servers. Even without support for non-synchronizing literals, cautious servers may handle invalid literal bytesize by closing the connection . However, servers which handle a non-synchronizing literal just like any other malformed command will enable this vulnerability. If a developer passes an unvalidated user-controlled input for one of these method arguments, an attacker can append CRLF sequence followed by a new IMAP command (like DELETE mailbox). Although this does not directly enable data exfiltration, it could be combined with other attack vectors or knowledge of the target system's attributes, e.g.: shared mail folders or the application's installed response handlers. Mitigation Update to a version of "net-imap" which validates server support for non-synchronizing literals before sending them. If upgrading "net-imap" is not possible: * Explicitly validate user-controlled inputs to prevent embedded non-synchronizing literals unless the server supports them. * For a simpler, more cautious approach: all embedded literals can be unconditionally prohibited, by checking that string inputs do not contain any CR or LF bytes. * Verify that the server advertises any of the "LITERAL+", "LITERAL-", or "IMAP4rev2" capabilities before using untrusted string inputs for the affected "raw data" arguments.
Publish Date: 2026-06-11
URL: CVE-2026-47240
Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Local
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: Required
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: None
- Integrity Impact: High
- Availability Impact: Low
For more information on CVSS3 Scores, click here.Type: Upgrade version
Release Date: 2026-06-11
Fix Resolution: https://github.com/ruby/net-imap.git - 0.5.15,net-imap - 0.6.4.1,net-imap - 0.5.15
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