net-imap vulnerable to denial of service via high iteration count for `SCRAM-*` authentication — CVE-2026-42256

Summary

### Summary When authenticating a connection with `SCRAM-SHA1` or `SCRAM-SHA256`, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. ### Details A hostile IMAP server can send an arbitrarily large PBKDF2 iteration count in the SCRAM server-first-message, causing the client to perform an expensive `OpenSSL::KDF.pbkdf2_hmac` call.…

Product

rubygems: net-imap

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Related advisories