Out-of-bounds write in libwebsockets
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- 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 HTTP/2 HPACK Path Header Parsing 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 parsing of HTTP/2 HPACK path header. 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-31036.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- 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
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Critical. 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 | — |
| Red Hat OpenStack Platform 17.1 | Affected | — |
| Red Hat Service Interconnect 2 | Affected | No fix yet |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-19773
- 2026-10-03 Alias added: GHSA-r4m8-276f-3r2f
- 2026-10-19 EPSS moved to the 50th–90th percentile
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-30 CVSS score added · Red Hat
References
Advisory 1
Other 1
More libwebsockets vulnerabilities
- TI-2026-84864 Out-of-bounds write in libwebsockets MQTT PUBACK handling CVSS 3.0HIGH 8.1
Sources
- CVE-2026-19773 · CVE Program
- CVE-2026-19773 · NVD
- FIRST EPSS
- GHSA-r4m8-276f-3r2f · GitHub Advisory Database · CC BY 4.0
- CVE-2026-19773 · 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