Vulnerability · Published Jun 28, 2026 · Assigned by VulnCheck
CVE-2026-58055nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length
Medium 5.4
In plain English
A medium-severity security flaw in nghttp2 from nghttp2. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 17% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
nghttp2's nghttpx proxy through 1.69.0 forwards an HTTP/1.1 Upgrade request that also carries a Content-Length header and body onto reusable keep-alive backend connections, re-adding the Upgrade and Connection headers while passing Content-Length verbatim. A backend that resolves the resulting ambiguous message in the attacker's favor enables HTTP request/response smuggling and cross-client response-queue poisoning.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | libnghttp2 | 1.68.0-3.el10_2.2 | ALSA-2026:54650 |
| AlmaLinux:8 | libnghttp2 | 1.33.0-6.el8_10.3 | ALSA-2026:55804 |
| AlmaLinux:9 | libnghttp2 | 1.43.0-6.el9_8.2 | ALSA-2026:54662 |
| AlmaLinux:10 | libnghttp2-devel | 1.68.0-3.el10_2.2 | ALSA-2026:54650 |
| AlmaLinux:8 | libnghttp2-devel | 1.33.0-6.el8_10.3 | ALSA-2026:55804 |
| AlmaLinux:9 | libnghttp2-devel | 1.43.0-6.el9_8.2 | ALSA-2026:54662 |
| AlmaLinux:10 | nghttp2 | 1.68.0-3.el10_2.2 | ALSA-2026:54650 |
| AlmaLinux:8 | nghttp2 | 1.33.0-6.el8_10.3 | ALSA-2026:55804 |
| AlmaLinux:9 | nghttp2 | 1.43.0-6.el9_8.2 | ALSA-2026:54662 |
| Alpine:v3.24 | nghttp2 | 1.70.0-r0 | ALPINE-CVE-2026-58055 |
| Debian:12 | nghttp2 | no fix listed | DEBIAN-CVE-2026-58055 |
| Debian:13 | nghttp2 | no fix listed | DEBIAN-CVE-2026-58055 |
| Debian:14 | nghttp2 | 1.70.0-1 | DEBIAN-CVE-2026-58055 |
| Rocky Linux:10 | nghttp2 | 0:1.68.0-3.el10_2.2 | RLSA-2026:54650 |
| Rocky Linux:8 | nghttp2 | 0:1.33.0-6.el8_10.3 | RLSA-2026:55804 |
| Rocky Linux:9 | nghttp2 | 0:1.43.0-6.el9_8.2 | RLSA-2026:54662 |
| Ubuntu:22.04:LTS | nghttp2 | 1.43.0-1ubuntu0.4 | UBUNTU-CVE-2026-58055 |
| Ubuntu:22.04:LTS | nghttp2 | 1.43.0-1ubuntu0.4 | USN-8495-1 |
| Ubuntu:24.04:LTS | nghttp2 | 1.59.0-1ubuntu0.4 | UBUNTU-CVE-2026-58055 |
| Ubuntu:24.04:LTS | nghttp2 | 1.59.0-1ubuntu0.4 | USN-8495-1 |
| Ubuntu:25.10 | nghttp2 | 1.64.0-1.1ubuntu1.2 | USN-8495-1 |
| Ubuntu:25.10 | nghttp2 | 1.64.0-1.1ubuntu1.2 | UBUNTU-CVE-2026-58055 |
| Ubuntu:26.04:LTS | nghttp2 | 1.68.0-2ubuntu0.2 | USN-8495-1 |
| Ubuntu:26.04:LTS | nghttp2 | 1.68.0-2ubuntu0.2 | UBUNTU-CVE-2026-58055 |
Affected products (as reported)
Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
References
- Proof of Concept exploit, third-party-advisory
- Fix commit (master) patch
- VulnCheck Advisory: nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length third-party-advisory