Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| libwebsockets | libwebsockets | b4b5aed3903eaff09cd76a410f69bbe5dff66f8e | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libwebsockets | 4.3.5-7 | — |
| Debian 13 | libwebsockets | 4.3.5-1+deb13u3 | — |
| Debian 12 | libwebsockets | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | libwebsockets | 4.3.5-3ubuntu1.2+esm1 | USN-8893-1 |
| Ubuntu Pro 24.04 LTS | libwebsockets | 4.3.3-1.1ubuntu0.1~esm3 | USN-8893-1 |
| Ubuntu Pro 22.04 LTS | libwebsockets | 4.0.20-2ubuntu1.1+esm2 | USN-8893-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | libwebsockets | 3.2.1-3ubuntu0.1~esm3 | USN-8893-1 |
| Ubuntu Pro 18.04 LTS | libwebsockets | 2.0.3-3ubuntu0.1~esm1 | USN-8893-1 |
| Ubuntu Pro 16.04 LTS | libwebsockets | 1.7.1-1ubuntu0.1~esm1 | USN-8893-1 |
Advisories 1
- USN-8893-1 libwebsockets vulnerabilities Ubuntu Security Notices (USN) · Oct 8, 2026
References
- ZDI-26-590
- vendor-provided URL vendor-advisory