# CVE-2026-19773: libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability

> Remote attackers can execute arbitrary code via an out-of-bounds write in libwebsockets HTTP/2 HPACK path header parsing without authentication.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-19773, GHSA-r4m8-276f-3r2f, UBUNTU-CVE-2026-19773, USN-8893-1

## What is CVE-2026-19773?

CVE-2026-19773 is a critical memory corruption vulnerability in libwebsockets, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-19773?


## How do I fix CVE-2026-19773?

Apply the vendor's patch.

## Is CVE-2026-19773 being exploited?

There is no known exploitation of CVE-2026-19773 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19773 and fix it if it is affected.

What it is: CVE-2026-19773 is a critical memory corruption vulnerability in libwebsockets, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-19773 in the wild and no public exploit code.

Affected product: libwebsockets. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19773/ (Markdown: https://insights.sbomify.com/CVE-2026-19773/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19773
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19773
- OSV: https://osv.dev/vulnerability/CVE-2026-19773

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19773/
Summaries are generated and may contain mistakes; the official description above is the record.