Security readout for executives and security teams
Plain-English summary
An authenticated MQTT v5 client could make Eclipse Mosquitto leak memory by sending a crafted CONNECT message. Over time, this could exhaust broker resources and disrupt MQTT service availability. The source bundle does not provide a CVSS score or confirmed exploitation evidence.
Executive priority
Treat this as an availability risk for MQTT-dependent operations, especially industrial, IoT, or telemetry environments. Prioritize inventory and vendor-guided remediation, but do not assume emergency exploitation without stronger evidence.
Technical view
CVE-2021-34431 is a CWE-401 memory leak in Eclipse Mosquitto versions 1.6 through 2.0.10. The trigger is a crafted MQTT v5 CONNECT message from an authenticated client, leading to potential denial of service against the broker.
Likely exposure
Exposure is limited to organizations running affected Eclipse Mosquitto broker versions with authenticated MQTT v5 clients. Risk increases where client identities are broadly provisioned or broker availability supports operational systems.
Exploitation context
The sources describe denial-of-service potential but do not cite public exploitation, weaponized tooling, or CISA KEV inclusion. Exploitation requires an authenticated client connection using MQTT v5.
Researcher notes
Key constraints are authenticated access and MQTT v5 CONNECT handling. The public bundle lacks CVSS details, exploit confirmation, and explicit remediation text, so validation should focus on version exposure, broker role criticality, and official Eclipse guidance.
Mitigation direction
- Identify all Eclipse Mosquitto broker versions in production and staging.
- Check Eclipse guidance and bug 573191 for fixed-release direction.
- Restrict broker access to trusted authenticated clients only.
- Monitor broker memory growth and availability symptoms.
- Review MQTT v5 client provisioning and revoke unnecessary credentials.
Validation and detection
- Confirm whether deployed Mosquitto versions are 1.6 through 2.0.10.
- Verify MQTT v5 is enabled or accepted by exposed brokers.
- Review broker logs for unusual authenticated CONNECT activity.
- Check memory telemetry for unexplained broker growth.
- Confirm remediation guidance against Eclipse Mosquitto sources.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-401: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-34431 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Missing Release of Memory after Effective Lifetime
Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.