golang.org/x/net/http2/h2c vulnerable to request smuggling attackGHSA-fxg5-wq6x-vr4w
HIGHGHSA-fxg5-wq6x-vr4w is a high-severity (CVSS 7.5) CWE-444 vulnerability in golang.org/x/net. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for golang.org/x/net — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fxg5-wq6x-vr4w.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
golang.org/x/netReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
A request smuggling attack is possible when using MaxBytesHandler. When using MaxBytesHandler, the body of an HTTP request is not fully consumed. When the server attempts to read HTTP2 frames from the connection, it will instead be reading the body of the HTTP request, which could be attacker-manipulated to represent arbitrary HTTP2 requests.
Specific Go Packages Affected
golang.org/x/net/http2/h2c
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/net | ≥ 0.0.0-20220524220425-1d687d428aca&&< 0.1.1-0.20221104162952-702349b0e862 | 0.1.1-0.20221104162952-702349b0e862go get golang.org/x/net@v0.1.1-0.20221104162952-702349b0e862 |
Affected Products
h2cgolangResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/net, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update golang.org/x/net to 0.1.1-0.20221104162952-702349b0e862 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fxg5-wq6x-vr4w is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This moderate severity flaw was found in golang.org/x/net/http2/h2c when using MaxBytesHandler. If the handler does not fully read the body of an HTTP request, the server may interpret the remaining request body as HTTP/2 frames. An attacker can craft this body to include arbitrary HTTP/2 frames, enabling request…
| Product | Fixed in | Advisory |
|---|---|---|
| MTA-6.2-RHEL-9 | mta/mta-hub-rhel9:6.2.0-16 | RHSA-2023:4627 |
| Red Hat OpenShift Container Platform 4.13 | openshift4/ose-thanos-rhel8:v4.13.0-202304190216.p0.gb6f11a5.assembly.stream | RHSA-2023:1326 |
Frequently Asked Questions
Is GHSA-fxg5-wq6x-vr4w in your dependencies?
Find it across Go, including transitive dependencies.