CVE-2026-19773
libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
9.8
libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
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.
- Record
CVE-2026-19773- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
EUVDEUVD-2026-79130
9.8
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.
- Record
EUVD-2026-79130- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-r4m8-276f-3r2f
9.8
libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution...
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.
- Record
GHSA-r4m8-276f-3r2f- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
NVD
9.8
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.
- Record
CVE-2026-19773- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
OSV
9.8
libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
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.
- Record
CVE-2026-19773- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-19773
9.8
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.
- Record
DEBIAN-CVE-2026-19773- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVOESA-2026-4076
7.3
libwebsockets security update
Libwebsockets (LWS) is a flexible, lightweight pure C library for implementing modern network protocols easily with a tiny footprint, using a nonblocking event loop.
Security Fix(es):
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.(CVE-2026-19773)
A vulnerability classified as critical was found in warmcat libwebsockets 4.5.0. The vulnerability is in the function report_raw_cbor in lib/misc/lecp.c when handling LECP CBOR recordings. This issue allows an out-of-bounds write (CWE-787), which could affect confidentiality, integrity, and availability. A proof-of-concept exploit is available.(CVE-2026-78161)
- Record
OESA-2026-4076- CVSS 3.1
- 7.3 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-19773
9.8
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.
- Record
UBUNTU-CVE-2026-19773- CVSS 3.0
- 9.8 Critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVUSN-8893-1 No score
libwebsockets vulnerabilities
It was discovered that libwebsockets did not properly validate user-supplied data when parsing HTTP/2 HPACK path headers, which could result in a write past the end of an allocated buffer. An attacker could possibly use this issue to execute arbitrary code. (CVE-2026-19773)
It was discovered that libwebsockets did not properly handle CBOR recording in the LECP parser, which could result in a write past the end of an allocated buffer. An attacker could possibly use this issue to cause a crash or execute arbitrary code. (CVE-2026-78161)
- Record
USN-8893-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
libwebsocketsDebian:12 |
All versions, plus listed versions 4.1.6-34.1.6-3.14.3.2-14.3.2-24.3.2-3 Show 12 moreShow less4.3.2-44.3.3-14.3.3-1.14.3.3-1.1~exp14.3.5-14.3.5-24.3.5-34.3.5-44.3.5-4.14.3.5-54.3.5-64.3.5-7 |
None known |
libwebsocketsDebian:13 |
before 4.3.5-1+deb13u3, plus listed versions 4.3.5-14.3.5-1+deb13u14.3.5-1+deb13u2 |
4.3.5-1+deb13u3 |
libwebsocketsDebian:14 |
before 4.3.5-7, plus listed versions 4.3.5-14.3.5-24.3.5-34.3.5-44.3.5-4.14.3.5-54.3.5-6 |
4.3.5-7 |
libwebsocketsopenEuler:24.03-LTS-SP1 |
before 4.3.3-8.oe2403sp1 | 4.3.3-8.oe2403sp1 |
libwebsocketsopenEuler:24.03-LTS-SP3 |
before 4.3.3-8.oe2403sp3 | 4.3.3-8.oe2403sp3 |
libwebsocketsopenEuler:24.03-LTS-SP4 |
before 4.3.3-8.oe2403sp4 | 4.3.3-8.oe2403sp4 |
libwebsocketsopenEuler:20.03-LTS-SP4 |
before 4.3.0-11.oe2003sp4 | 4.3.0-11.oe2003sp4 |
libwebsocketsopenEuler:22.03-LTS-SP4 |
before 4.3.0-11.oe2203sp4 | 4.3.0-11.oe2203sp4 |
libwebsocketsUbuntu:Pro:16.04:LTS |
before 1.7.1-1ubuntu0.1~esm1, plus listed versions 1.2.2-11.6.0-31.6.0-41.6.0-51.6.1-11.7.0-1ubuntu11.7.0-21.7.1-1 |
1.7.1-1ubuntu0.1~esm1 |
libwebsocketsUbuntu:Pro:18.04:LTS |
before 2.0.3-3ubuntu0.1~esm1, plus listed versions 2.0.3-32.0.3-3build1 |
2.0.3-3ubuntu0.1~esm1 |
Show 4 moreShow less
| Package | Affected | Fixed |
|---|---|---|
libwebsocketsUbuntu:Pro:20.04:LTS |
before 3.2.1-3ubuntu0.1~esm3, plus listed versions 2.0.3-3build13.2.1-33.2.1-3ubuntu0.1~esm13.2.1-3ubuntu0.1~esm2 |
3.2.1-3ubuntu0.1~esm3 |
libwebsocketsUbuntu:Pro:22.04:LTS |
before 4.0.20-2ubuntu1.1+esm2, plus listed versions 4.0.20-24.0.20-2ubuntu14.0.20-2ubuntu1.14.0.20-2ubuntu1.1+esm1 |
4.0.20-2ubuntu1.1+esm2 |
libwebsocketsUbuntu:Pro:24.04:LTS |
before 4.3.3-1.1ubuntu0.1~esm3, plus listed versions 4.3.2-44.3.3-14.3.3-1.1build14.3.3-1.1build24.3.3-1.1build34.3.3-1.1ubuntu0.1~esm14.3.3-1.1ubuntu0.1~esm2 |
4.3.3-1.1ubuntu0.1~esm3 |
libwebsocketsUbuntu:Pro:26.04:LTS |
before 4.3.5-3ubuntu1.2+esm1, plus listed versions 4.3.5-14.3.5-34.3.5-3ubuntu14.3.5-3ubuntu1.1 |
4.3.5-3ubuntu1.2+esm1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-19773 is a critical vulnerability (CVSS 9.8) in Libwebsockets, published September 15, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.65%, the 51st percentile. Fixed in libwebsockets 4.3.5-1+deb13u3.
References
zerodayinitiative.com/advisories/ZDI-26-590
github.com/warmcat/libwebsockets/commit/824151862f37bc72f46d9a3e01d5b9408d313a0b
nvd.nist.gov/vuln/detail/CVE-2026-19773
github.com/advisories/GHSA-r4m8-276f-3r2f
github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19773.json
security-tracker.debian.org/tracker/CVE-2026-19773