CVE-2025-43857

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of service disruption.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-04-28 16:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 09:24 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 6.0 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-04-28 16:15 UTC

Last modified

2026-06-17 09:24 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-400 · Uncontrolled resource consumption

Record status

Analyzed

Affected

• ruby-lang net\ < 0.2.5
• ruby-lang net\ < 0.3.9
• ruby-lang net\ < 0.4.20
• ruby-lang net\ < 0.5.7

Attack profile CVSS 4.0 · 6.0

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

Passive

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-43857.md and follow it. Check whether this project is affected by CVE-2025-43857. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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