RCE in Ruby Net-imap
CVE-2026-42258
Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.4.24, 0.5.14, and 0.6.4, symbol arguments to commands are vulnerable to a CRLF Injection / IMAP Command injection via Symbol arg…
Vulnerability class: Command Injection (OS Command Injection)
EPSS: 0.001 (25.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Ruby Net-imap — versions < 0.4.24, >= 0.5.0, < 0.5.14, >= 0.6.0, < 0.6.4
- Ruby-lang Net\ — versions \
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-42258?
- CVE-2026-42258 is a critical-severity vulnerability in Ruby Net-imap, classified under Command Injection. CVSS score: 9.8/10. Published 2026-05-09.
- How severe is CVE-2026-42258?
- Critical severity. CVSS v3 base score is 9.8 out of 10.