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Vulnerability record · CVE-2025-43857 · published 28 April 2025

CVE-2025-43857: Ruby-lang net\ uncontrolled resource consumption vulnerability

Ruby Lang · Net\

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.

6.0 CVSS 4.0 Medium EPSS 0.49% · top 60.3% CWE-400 · Uncontrolled resource consumptionCWE-405 · CWE-405
6.0CVSS 4.0 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/ruby/net-imap/pull/442 Issue TrackingPatch
https://github.com/ruby/net-imap/pull/444/commits/0ae8576c1a90bcd9573f81bdad4b4b824642d105#diff-53721cb4d9c3fb86b95cc847 Patch
https://github.com/ruby/net-imap/pull/445 Issue TrackingPatch
https://github.com/ruby/net-imap/pull/446 Issue TrackingPatch
https://github.com/ruby/net-imap/pull/447 Issue TrackingPatch
https://github.com/ruby/net-imap/security/advisories/GHSA-j3g3-5qv5-52mj Vendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2025-43857), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.