CVE-2021-41039

Exp

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Published: 2021-12-01 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-41039 is rated High Exploit Risk (69/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.26%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.01% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2021-41039

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-41039

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 0.25% 1.26% +1.01%
2 2025-12-28 0.24% 0.25% +0.01%
3 2025-12-27 — 0.24% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-41039

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]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-41039

OS Trackers for CVE-2021-41039

vendor priority summary link
alpine high CVE-2021-41039: 1 source package rows (mosquitto); 18 state rows across 7 repos (3.11-main, 3.12-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 18. https://security.alpinelinux.org/vuln/CVE-2021-41039
debian not yet assigned CVE-2021-41039 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-2021-41039
ubuntu medium CVE-2021-41039 medium priority: Ubuntu including 1 source packages (mosquitto), 14 status rows across 14 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 8, ignored 3, released 3. https://ubuntu.com/security/CVE-2021-41039

Affected software / configurations for CVE-2021-41039

Vendor Product Version Raw CPE
eclipse mosquitto >= 1.6, <= 2.0.11 cpe:2.3:a:eclipse:mosquitto:*:*:*:*:*:*:*:*

References for CVE-2021-41039

cvelogic Threat Intelligence