Possible DoS by memory exhaustion in net-imap

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.0 · 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 · score source

EPSS

• CVE-2025-25186: 0.63% estimated exploitation activity in the next 30 days; percentile 50.06 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary There is a possibility for denial of service by memory exhaustion in net-imap's response parser. At any time while the client is connected, a malicious server can send can send highly compressed uid-set data which is automatically read by the client's receiver thread. The response parser uses Range#toa to convert the uid-set data into arrays of integers, with no limitation on the expanded size of the ranges. Details IMAP's uid-set and sequence-set formats can compress ranges of numbers, for example: "1,2,3,4,5" and "1:5" both represent the same set. When Net::IMAP::ResponseParser receives APPENDUID or COPYUID response codes, it expands each uid-set into an array of integers. On a 64 bit system, these arrays will expand to 8 bytes for each number in the set. A malicious IMAP server may send specially crafted APPENDUID or COPYUID responses with very large uid-set ranges. The Net::IMAP client parses each server response in a separate thread, as soon as each responses is received…

Published by the source

10 Feb 2025, 17:42 UTC

Last modified by the source

30 Apr 2025, 20:43 UTC

Source last checked

26 Oct 2026, 15:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-7fc5-f82f-cx69

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# Patch Next advisory brief: CVE-2025-25186

Advisory: Possible DoS by memory exhaustion in net-imap
IDs: CVE-2025-25186, GHSA-7fc5-f82f-cx69
Record: https://patchnext.com/advisories/cve-2025-25186 (revision 1, source checked 26 Oct 2026, 15:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: net-imap 0.5.6, 0.4.19, 0.3.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems net-imap: affected >= 0.3.2, < 0.3.8; >= 0.4.0, < 0.4.19; >= 0.5.0, < 0.5.6; fixed in 0.4.19, 0.5.6, 0.3.8

## Suggested inspection (read-only)
- RubyGems net-imap: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on net-imap.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-7fc5-f82f-cx69 (GitHub-reviewed advisory GHSA-7fc5-f82f-cx69 lists affected ranges: RubyGems net-imap >=0.3.2 =0.4.0 =0.5.0 <0.5.6)

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