Out-of-bounds write in libwebsockets MQTT PUBACK handling
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- No fix listed
Attack profile from CVSS 3.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-787 and the CVSS impact.
Summary
libwebsockets is affected from commit b4b5aed3903eaff09cd76a410f69bbe5dff66f8e. The flaw is in handling of MQTT PUBACK packets, where missing validation of user-supplied data lets a write go past the end of an allocated buffer (CWE-787). A remote attacker can execute arbitrary code in the context of the current process without authentication.
Written with Claude Haiku 5.5 from the sources below · 2026-11-04
Description from the CNA
libwebsockets MQTT Protocol PUBACK Packet Handling Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of libwebsockets. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of PUBACK packets. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-31039.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| libwebsockets | libwebsockets | b4b5aed3903eaff09cd76a410f69bbe5dff66f8e | — | No fix listed | CNA |
- libwebsockets Vendorlibwebsockets Affected b4b5aed3903eaff09cd76a410f69bbe5dff66f8e Fixed in — No fix listed CNA
Remediation
The sources list no fixed version for libwebsockets. Red Hat lists A-MQ Interconnect 1, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1 and Red Hat Service Interconnect 2 as affected with no available fix plan.
Written with Claude Haiku 5.5 from the sources below · 2026-11-04
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| A-MQ Interconnect 1 | Affected | No fix yet |
| Red Hat OpenStack Platform 16.2 | Affected | No fix yet |
| Red Hat OpenStack Platform 17.1 | Affected | No fix yet |
| Red Hat Service Interconnect 2 | Affected | No fix yet |
Timeline
- 2026-11-03 Threatist record created from CVE-2026-114550
- 2026-11-04 Affected versions changed · Red Hat
- 2026-11-04 CVSS score added · Red Hat
- 2026-11-04 Alias added: GHSA-64rj-2w6g-r32v
- 2026-11-05 Priority changed: MEDIUM → LOW
- 2026-11-06 CISA SSVC decision points changed
References
Advisory 1
Other 1
More libwebsockets vulnerabilities
- TI-2026-16038 Out-of-bounds write in libwebsockets CVSS 3.0CRITICAL 9.8
Sources
- CVE-2026-114550 · CVE Program
- CVE-2026-114550 · NVD
- FIRST EPSS
- GHSA-64rj-2w6g-r32v · GitHub Advisory Database · CC BY 4.0
- CVE-2026-114550 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences