# CVE-2026-58055: nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length > Attackers can exploit HTTP request smuggling in nghttpx proxy to poison response queues and access or modify data across clients. - **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:L/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 28 Jun 2026 - **Updated:** 29 Jun 2026 - **Also known as:** ALPINE-CVE-2026-58055, ALSA-2026:54650, ALSA-2026:54662, ALSA-2026:55804, AZL-91451, BELL-CVE-2026-58055, CLSA-2026-1787308423, CLSA-2026-1787754280, DEBIAN-CVE-2026-58055, ECHO-401a-73df-0d29, GHSA-xrr7-82jr-v58x, JLSEC-2026-1157, MGASA-2026-0309, MINI-wgg3-56h4-pc44, OESA-2026-2977, OESA-2026-2978, OESA-2026-2979, OESA-2026-2980, RHSA-2026:35454, RHSA-2026:52414, RHSA-2026:54650, RHSA-2026:54662, RHSA-2026:55804, RLSA-2026:54650, RLSA-2026:54662, RLSA-2026:55804, ROOT-OS-DEBIAN-12-CVE-2026-58055, ROOT-OS-DEBIAN-13-CVE-2026-58055, SUSE-SU-2026:22594-1, SUSE-SU-2026:22630-1, SUSE-SU-2026:22707-1, SUSE-SU-2026:22893-1, SUSE-SU-2026:2883-1, SUSE-SU-2026:3153-1, SUSE-SU-2026:3154-1, SUSE-SU-2026:4029-1, UBUNTU-CVE-2026-58055, USN-8495-1, openSUSE-SU-2026:11156-1, openSUSE-SU-2026:21302-1 ## What is CVE-2026-58055? CVE-2026-58055 is a medium-severity vulnerability in nghttp2, published on 28 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### 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. Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests) ## Which versions are affected by CVE-2026-58055? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `libnghttp2` | AlmaLinux:10 | All versions | 1.68.0-3.el10_2.2 | | `libnghttp2-devel` | AlmaLinux:10 | All versions | 1.68.0-3.el10_2.2 | | `nghttp2` | AlmaLinux:10 | All versions | 1.68.0-3.el10_2.2 | | `libnghttp2` | AlmaLinux:8 | All versions | 1.33.0-6.el8_10.3 | | `libnghttp2-devel` | AlmaLinux:8 | All versions | 1.33.0-6.el8_10.3 | | `nghttp2` | AlmaLinux:8 | All versions | 1.33.0-6.el8_10.3 | | `libnghttp2` | AlmaLinux:9 | All versions | 1.43.0-6.el9_8.2 | | `libnghttp2-devel` | AlmaLinux:9 | All versions | 1.43.0-6.el9_8.2 | | `nghttp2` | AlmaLinux:9 | All versions | 1.43.0-6.el9_8.2 | | `libnghttp2` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.68.0-3.el10_2.2 | | `libnghttp2-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.68.0-3.el10_2.2 | | `libnghttp2-devel` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.68.0-3.el10_2.2 | | `nghttp2` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.68.0-3.el10_2.2 | | `nghttp2-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.68.0-3.el10_2.2 | | `nghttp2-debugsource` | Red Hat:enterprise_linux:10.2 | All versions | 0:1.68.0-3.el10_2.2 | | `libnghttp2` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1.33.0-6.el8_10.3 | | `libnghttp2-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1.33.0-6.el8_10.3 | | `nghttp2` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1.33.0-6.el8_10.3 | | `nghttp2-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1.33.0-6.el8_10.3 | | `nghttp2-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:1.33.0-6.el8_10.3 | | `libnghttp2-debuginfo` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.33.0-6.el8_10.3 | | `libnghttp2-devel` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.33.0-6.el8_10.3 | | `nghttp2` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.33.0-6.el8_10.3 | | `nghttp2-debuginfo` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.33.0-6.el8_10.3 | | `nghttp2-debugsource` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.33.0-6.el8_10.3 | | `libnghttp2` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.43.0-6.el9_8.2 | | `libnghttp2-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.43.0-6.el9_8.2 | | `nghttp2` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.43.0-6.el9_8.2 | | `nghttp2-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.43.0-6.el9_8.2 | | `nghttp2-debugsource` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1.43.0-6.el9_8.2 | | `libnghttp2-debuginfo` | Red Hat:enterprise_linux:9::crb | All versions | 0:1.43.0-6.el9_8.2 | | `libnghttp2-devel` | Red Hat:enterprise_linux:9::crb | All versions | 0:1.43.0-6.el9_8.2 | | `nghttp2` | Red Hat:enterprise_linux:9::crb | All versions | 0:1.43.0-6.el9_8.2 | | `nghttp2-debuginfo` | Red Hat:enterprise_linux:9::crb | All versions | 0:1.43.0-6.el9_8.2 | | `nghttp2-debugsource` | Red Hat:enterprise_linux:9::crb | All versions | 0:1.43.0-6.el9_8.2 | | `libnghttp2` | Red Hat:hummingbird:1 | All versions | 0:1.69.0-3.1.hum1 | | `libnghttp2` | Red Hat:hummingbird:1 | All versions | 0:1.69.0-5.hum1 | | `libnghttp2-devel` | Red Hat:hummingbird:1 | All versions | 0:1.69.0-3.1.hum1 | | `libnghttp2-devel` | Red Hat:hummingbird:1 | All versions | 0:1.69.0-5.hum1 | | `mingw32-libnghttp2` | Red Hat:hummingbird:1 | All versions | 0:1.69.0-3.1.hum1 | Products: Nghttp2 Nghttp2. ## How do I fix CVE-2026-58055? Apply the vendor's patch. ## Is CVE-2026-58055 being exploited? There is no known exploitation of CVE-2026-58055 in the wild and no public exploit code. ## Other vulnerabilities in nghttp2 - [CVE-2026-27135](https://insights.sbomify.com/CVE-2026-27135/): nghttp2 Denial of service: Assertion failure due to the missing state validation (high 7.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-58055 and fix it if it is affected. What it is: CVE-2026-58055 is a medium-severity vulnerability in nghttp2, published on 28 Jun 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-2026-58055 in the wild and no public exploit code. Affected product: nghttp2. 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-2026-58055/ (Markdown: https://insights.sbomify.com/CVE-2026-58055/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58055 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58055 - OSV: https://osv.dev/vulnerability/CVE-2026-58055 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-58055/ Summaries are generated and may contain mistakes; the official description above is the record.