GHSA-g754-hx8w-x2g6 is a medium-severity (CVSS 5.3) CWE-770 vulnerability in github.com/quic-go/quic-go. A fix is available for github.com/quic-go/quic-go — see the affected versions and patch details below.
quic-go HTTP/3 QPACK Header Expansion DoS
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-g754-hx8w-x2g6.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-g754-hx8w-x2g6 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/quic-go/quic-goReal-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
Summary
An attacker can cause excessive memory allocation in quic-go's HTTP/3 client and server implementations by sending a QPACK-encoded HEADERS frame that decodes into a large header field section (many unique header names and/or large values). The implementation builds an http.Header (used on the http.Request and http.Response, respectively), while only enforcing limits on the size of the (QPACK-compressed) HEADERS frame, but not on the decoded header, leading to memory exhaustion.
Impact
A misbehaving or malicious peer can cause a denial-of-service (DoS) attack on quic-go's HTTP/3 servers or clients by triggering excessive memory allocation, potentially leading to crashes or exhaustion. It affects both servers and clients due to symmetric header construction.
Details
In HTTP/3, headers are compressed using QPACK (RFC 9204). quic-go's HTTP/3 server (and client) decodes the QPACK-encoded HEADERS frame into header fields, then constructs an http.Request (or response).
http3.Server.MaxHeaderBytes and http3.Transport.MaxResponseHeaderBytes, respectively, limit encoded HEADERS frame size (default: 1 MB server, 10 MB client), but not decoded size. A maliciously crafted HEADERS frame can expand to ~50x the encoded size using QPACK static table entries with long names / values.
RFC 9114 requires enforcing decoded field section size limits via SETTINGS, which quic-go did not do.
The Fix
quic-go now enforces RFC 9114 decoded field section size limits, sending SETTINGS_MAX_FIELD_SECTION_SIZE and using incremental QPACK decoding to check the header size after each entry, aborting early on violations with HTTP 431 (on the server side) and stream reset (on the client side).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/quic-go/quic-go | all versions | 0.57.0go get github.com/quic-go/quic-go@v0.57.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/quic-go/quic-go, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/quic-go/quic-go to 0.57.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g754-hx8w-x2g6 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-g754-hx8w-x2g6 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-g754-hx8w-x2g6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-g754-hx8w-x2g6 in your dependencies?
O3 Security finds GHSA-g754-hx8w-x2g6 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.