CVE-2026-42246
highpriority · track · 30EPSS 0.003 · 24 %ileDEEURUUSEPSS · scored 2026-10-26
Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to return "successfully", without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.9–7.6
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (53)
Products and version ranges known to be affected.
advisories (4)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-2117HCL BigFix Compliance (Ruby): Mehrere SchwachstellenDeutsch2026-06-28csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in HCL BigFix Compliance ausnutzen, um beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand herbeizuführen.
- WID-SEC-W-2026-2163Red Hat Enterprise Linux (ruby: net-imap): Mehrere SchwachstellenDeutsch2026-06-30csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Red Hat Enterprise Linux ausnutzen, um einen Denial of Service Angriff durchzuführen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren oder vertrauliche Informationen offenzulegen.
- WID-SEC-W-2026-2379Ruby: Mehrere SchwachstellenDeutsch2026-07-15csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Ruby ausnutzen, um Informationen offenzulegen, um einen Denial of Service Angriff durchzuführen, und um beliebigen Programmcode auszuführen.
- GHSA-vcgp-9326-pqcpnet-imap vulnerable to STARTTLS stripping via invalid response timing2026-05-04ghsa · osvUS
### Summary A man-in-the-middle attacker can cause `Net::IMAP#starttls` to return "successfully", without starting TLS. ### Details When using `Net::IMAP#starttls` to upgrade a plaintext connection to use TLS, a man-in-the-middle attacker can inject a tagged `OK` response with an easily predictable tag. By sending the response before the client finishes sending the command, the command completes "successfully" before the response handler is registered. This allows `#starttls` to return without error, but the response handler is never invoked, the TLS connection is never established, and the socket remains unencrypted. This allows man-in-the-middle attackers to perform a STARTTLS stripping attack, unless the client code explicitly checks `Net::IMAP#tls_verified?`. ### Impact TLS bypass, leading to cleartext transmission of sensitive information. ### Mitigation * Upgrade to a patched version of net-imap that raises an exception whenever `#starttls` does not establish TLS. * Connect to an implicit TLS port, rather than use `STARTTLS` with a cleartext port. This is strongly recommended anyway: * [RFC 8314](https://www.rfc-editor.org/info/rfc8314): Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access * [NO STARTTLS](https://nostarttls.secvuln.info/): Why TLS is better without STARTTLS, A Security Analysis of STARTTLS in the Email Context * Explicitly verify `Net::IMAP#tls_verified?` is `true`, before using the connection after `#starttls`.
also known as (4)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (41)
External citations — patches, advisories, analysis.
- https://github.com/ruby/net-imap/releases/Patchcnnvd
- https://nvd.nist.gov/vuln/detail/CVE-2026-42246cnnvd
- https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618enisa_euvd
- https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485eenisa_euvd
- https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42cenisa_euvd
- https://github.com/ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873daenisa_euvd
- https://github.com/ruby/net-imap/releases/tag/v0.3.10enisa_euvd
- https://github.com/ruby/net-imap/releases/tag/v0.4.24enisa_euvd
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