CVE-2025-43857: net-imap rubygem vulnerable to possible DoS by memory exhaustion
Description
Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.5.7, 0.4.20, 0.3.9, and 0.2.5, there is a possibility for denial of service by memory exhaustion when net-imap reads server responses. At any time while the client is connected, a malicious server can send can send a "literal" byte count, which is automatically read by the client's receiver thread. The response reader immediately allocates memory for the number of bytes indicated by the server response. This should not be an issue when securely connecting to trusted IMAP servers that are well-behaved. It can affect insecure connections and buggy, untrusted, or compromised servers (for example, connecting to a user supplied hostname). This issue has been patched in versions 0.5.7, 0.4.20, 0.3.9, and 0.2.5.
Classification
CVE ID: CVE-2025-43857
CVSS Base Severity: MEDIUM
CVSS Base Score: 6.0
CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Problem Types
CWE-400: Uncontrolled Resource Consumption CWE-770: Allocation of Resources Without Limits or Throttling CWE-789: Memory Allocation with Excessive Size Value CWE-405: Asymmetric Resource Consumption (Amplification)Affected Products
Vendor: ruby
Product: net-imap
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.08% (probability of being exploited)
EPSS Percentile: 23.65% (scored less or equal to compared to others)
EPSS Date: 2025-05-27 (when was this score calculated)
References
https://nvd.nist.gov/vuln/detail/CVE-2025-43857https://github.com/ruby/net-imap/security/advisories/GHSA-j3g3-5qv5-52mj
https://github.com/ruby/net-imap/pull/442
https://github.com/ruby/net-imap/pull/444/commits/0ae8576c1a90bcd9573f81bdad4b4b824642d105#diff-53721cb4d9c3fb86b95cc8476ca2df90968ad8c481645220c607034399151462
https://github.com/ruby/net-imap/pull/445
https://github.com/ruby/net-imap/pull/446
https://github.com/ruby/net-imap/pull/447