CVE-2021-34434: eclipse mosquitto Improper Authorization
Vulnerability summary
CVE-2021-34434 is a medium (CVSS 5.3) Improper Authorization vulnerability in eclipse mosquitto. EPSS estimates a 1.33% chance of exploitation in the next 30 days, higher than 71% of scored vulnerabilities. 1 public exploit is recorded.
Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 1Timeline
- 30-08-2021PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
Description
In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- OSV · DebianEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS trend
Probability
1.33%
Chance of exploitation in the next 30 days
Percentile
71%
Versus all other CVEs
30-day change
No change 0.00 pp
From 1.33% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundExploit Reference (bugs.eclipse.org)
Maturity: unknown
Weaknesses
CWE · root cause- CWE-285Improper AuthorizationThe product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
- CWE-863Incorrect AuthorizationThe product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Debian1 product
- mosquitto< 2.0.11-1.2+deb12u1 | < 2.0.15-1
Eclipse1 product
- mosquitto≥ 2.0.0, ≤ 2.0.11
Fedoraproject1 product
- fedoraEOL34 | 35
Mageia1 product
- mosquitto< 2.0.12-1.mga8
The eclipse foundation1 product
- eclipse mosquitto≥ 2.0, < unspecified | ≥ unspecified, ≤ 2.0.11
Ubuntu1 product
- mosquitto< 2.0.11-1ubuntu1.1
6 vendors · 6 products
References
11 links- lists.fedoraproject.org/archives/…Vendor Advisory
- lists.fedoraproject.org/archives/…Vendor Advisory
www.debian.org/security/2023/dsa-5511Vendor Advisory