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CVE-2025-43857

21
FAUCET Score

CVE-2025-43857 is a denial-of-service vulnerability affecting the Net::IMAP client functionality in Ruby, specifically versions prior to 0.5.7, 0.4.20, 0.3.9, and 0.2.5. A malicious IMAP server can trigger memory exhaustion by sending a large "literal" byte count, causing the client to immediately allocate excessive memory. This vulnerability has a CVSS score of 6.5 (Medium), indicating it can be exploited remotely with low attack complexity, requiring no privileges, but does involve user interaction (connecting to a malicious server) and results in high availability impact. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.2.5CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
>= 0.3.0, < 0.3.9CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
>= 0.4.0, < 0.4.20CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
>= 0.5.0, < 0.5.7CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*

CVSS Data

CVSS version used by this source: 4.0

6.0MEDIUM

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:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
PASSIVE
VS Confidentiality
NONE
VS Integrity
NONE
VS Availability
HIGH
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.44%
Probability of exploitation in next 30 days
EPSS Percentile
35.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0044 is in the 38th percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (10)

github_advisorypatch availablevia nvd_reference
View patch
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.5.7
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.4.20
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.3.9
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.2.5
redhatvendor investigatingvia redhat_api
Product: Logging Subsystem for Red Hat OpenShiftFixed in: openshift-logging/fluentd-rhel9
redhatvendor investigatingvia redhat_api
Product: Red Hat 3scale API Management Platform 2Fixed in: 3scale-amp2/zync-rhel9
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: ruby
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: ruby:3.3/ruby
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: ruby:3.3/ruby

Vendor Advisories (3)

redhatCVE-2025-43857Moderate

net-imap: net-imap rubygem vulnerable to possible DoS by memory exhaustion

Apr 28, 2025
rubygemsGHSA-j3g3-5qv5-52mjmedium

net-imap rubygem vulnerable to possible DoS by memory exhaustion

Apr 28, 2025
microsoft2025-Apr/CVE-2025-43857Important

net-imap rubygem vulnerable to possible DoS by memory exhaustion

Apr 8, 2025

References

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