{"schema_version":"1.9.0","id":"GHSA-8p34-64r3-mwg8","published":"2026-06-09T18:36:04Z","modified":"2026-09-10T03:51:08.225147750Z","aliases":["CVE-2026-47240"],"summary":"Net::IMAP: Command Injection via non-synchronizing literal in \"raw\" argument","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.\n\n### Details\n\nRaw 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.\n\nServers 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.\n\nThis affects the following commands' string arguments:\n* `criteria` for `#search` and `#uid_search`\n* `search_keys` for `#sort`, `#thread`, `#uid_sort`, and `#uid_thread`\n* `attr` for `#fetch` and `#uid_fetch`\n\nPrior 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).\n\n### Impact\n\nFortunately, `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.\n\nIf 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.\n\n### Mitigation\n\nUpdate to a version of `net-imap` which validates server support for non-synchronizing literals before sending them.\n\nIf upgrading `net-imap` is not possible:\n* Explicitly validate user-controlled inputs to prevent embedded non-synchronizing literals unless the server supports them.\n* 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.\n* Verify that the server advertises any of the `LITERAL+`, `LITERAL-`, or `IMAP4rev2` capabilities before using untrusted string inputs for the affected \"raw data\" arguments.","affected":[{"package":{"name":"net-imap","ecosystem":"RubyGems","purl":"pkg:gem/net-imap"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.6.0"},{"fixed":"0.6.4.1"}]}],"versions":["0.6.0","0.6.1","0.6.2","0.6.3","0.6.4"],"database_specific":{"last_known_affected_version_range":"<= 0.6.4","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-8p34-64r3-mwg8/GHSA-8p34-64r3-mwg8.json"}},{"package":{"name":"net-imap","ecosystem":"RubyGems","purl":"pkg:gem/net-imap"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.15"}]}],"versions":["0.1.0","0.1.1","0.2.0","0.2.1","0.2.2","0.2.3","0.2.4","0.2.5","0.3.0","0.3.1","0.3.10","0.3.2","0.3.3","0.3.4","0.3.4.1","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.1","0.4.10","0.4.11","0.4.12","0.4.13","0.4.14","0.4.15","0.4.16","0.4.17","0.4.18","0.4.19","0.4.2","0.4.20","0.4.21","0.4.22","0.4.23","0.4.24","0.4.25","0.4.3","0.4.4","0.4.5","0.4.6","0.4.7","0.4.8","0.4.9","0.4.9.1","0.5.0","0.5.1","0.5.10","0.5.11","0.5.12","0.5.13","0.5.14","0.5.2","0.5.3","0.5.4","0.5.5","0.5.6","0.5.7","0.5.8","0.5.9"],"database_specific":{"last_known_affected_version_range":"<= 0.5.14","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-8p34-64r3-mwg8/GHSA-8p34-64r3-mwg8.json"}}],"references":[{"type":"WEB","url":"https://github.com/ruby/net-imap/security/advisories/GHSA-8p34-64r3-mwg8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47240"},{"type":"PACKAGE","url":"https://github.com/ruby/net-imap"},{"type":"WEB","url":"https://github.com/ruby/net-imap/releases/tag/v0.6.4.1"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/net-imap/CVE-2026-47240.yml"},{"type":"WEB","url":"https://www.cve.org/CVERecord?id=CVE-2026-47240"}],"database_specific":{"cwe_ids":["CWE-77","CWE-93"],"github_reviewed":true,"github_reviewed_at":"2026-06-09T18:36:04Z","nvd_published_at":"2026-06-22T21:16:24Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N"}]}