CVE-2023-5632 | Unconditionally adding an event to the epoll causes excessive CPU consumption

In Eclipse Mosquito before and including 2.0.5, establishing a connection to the mosquitto server without sending data causes the EPOLLOUT event to be added, which results excessive CPU consumption. This could be used by a malicious actor to perform denial of service type attack. This issue is fixed in 2.0.6

Published: 2023-10-18 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-5632 is rated Moderate Risk (47.3/100): CVSS High severity, with low exploitation likelihood (EPSS 0.69%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-5632

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.09% 0.69% +0.60%
2 2025-11-21 0.36% 0.09% -0.26%
3 2025-11-18 — 0.36% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-5632

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2023-5632

OS Trackers for CVE-2023-5632

vendor priority summary link
alpine — CVE-2023-5632: 1 source package rows (mosquitto); 30 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 30. https://security.alpinelinux.org/vuln/CVE-2023-5632
debian not yet assigned CVE-2023-5632 not yet assigned priority: Debian including 1 source packages (mosquitto), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-5632
redhat medium — https://access.redhat.com/security/cve/CVE-2023-5632
suse medium — https://www.suse.com/security/cve/CVE-2023-5632/
ubuntu medium CVE-2023-5632 medium priority: Ubuntu including 1 source packages (mosquitto), 8 status rows across 8 suites (bionic, focal, jammy, lunar, mantic, trusty, upstream, xenial): not-affected 7, released 1. https://ubuntu.com/security/CVE-2023-5632

Affected software / configurations for CVE-2023-5632

Vendor Product Version Raw CPE
eclipse mosquitto 2.0.5 cpe:2.3:a:eclipse:mosquitto:2.0.5:*:*:*:*:*:*:*

References for CVE-2023-5632

cvelogic Threat Intelligence