CyberSecBulletin
CVE-2026-42245NVD status: Analyzed

net-imap: Inefficient Algorithmic Complexity

Published Updated By the CyberSecBulletin desk

CVE-2026-42245 is a high-severity inefficient algorithmic complexity vulnerability in net-imap from Ruby, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected net-imap versions: < 0.4.24; >= 0.5.0, < 0.5.14; >= 0.6.0, < 0.6.4. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.41% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Net to 0.4.24 or 0.5.14 or 0.6.4, whichever matches your release line, or a later version.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Rubynet-imap< 0.4.24; >= 0.5.0, < 0.5.14; >= 0.6.0, < 0.6.4Not stated
Ruby-langNetbefore 0.4.24; 0.5.0 up to, but not including, 0.5.14; 0.6.0 up to, but not including, 0.6.40.4.24, 0.5.14, 0.6.4

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.02.3LowCNA (github.com)
CVSS 3.17.5HighNVD

Official description

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, Net::IMAP::ResponseReader has quadratic time complexity when reading large responses containing many string literals. A hostile server can send responses which are crafted to exhaust the client's CPU for a denial of service attack. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Inefficient Algorithmic Complexity

An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

More Inefficient Algorithmic Complexity vulnerabilities (CWE-407)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in net-imap

All net-imap vulnerabilities

Recent Inefficient Algorithmic Complexity vulnerabilities

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