GHSA-5h46-h7hh-c6x9 — hyper
MEDIUMGHSA-5h46-h7hh-c6x9 is a medium-severity (CVSS 5.9) CWE-190 vulnerability in hyper. 1 public exploit reference exists, so weaponization risk is real. A fix is available for hyper — see the affected versions and patch details below.
Integer Overflow in Chunked Transfer-Encoding
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-5h46-h7hh-c6x9 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 376,715 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
hyperReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
hyper's HTTP server and client code had a flaw that could trigger an integer overflow when decoding chunk sizes that are too big. This allows possible data loss, or if combined with an upstream HTTP proxy that allows chunk sizes larger than hyper does, can result in "request smuggling" or "desync attacks".
Vulnerability
Example:
GET / HTTP/1.1
Host: example.com
Transfer-Encoding: chunked
f0000000000000003
abc
0
hyper only reads the rightmost 64-bit integer as the chunk size. So it reads f0000000000000003 as 3. A loss of data can occur since hyper would then read only 3 bytes of the body. Additionally, an HTTP request smuggling vulnerability would occur if using a proxy which instead has prefix truncation in the chunk size, or that understands larger than 64-bit chunk sizes.
Read more about desync attacks: https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn
Impact
To determine if vulnerable to data loss, these things must be true:
- Using HTTP/1.1. Since HTTP/2 does not use chunked encoding, it is not vulnerable.
- Using hyper as a server or client. The body would be improperly truncated in either case.
- Users send requests or responses with chunk sizes greater than 18 exabytes.
To determine if vulnerable to desync attacks, these things must be true:
- Using an upstream proxy that allows chunks sizes larger than 64-bit. If the proxy rejects chunk sizes that are too large, that request won't be forwarded to hyper.
Patches
We have released the following patch versions:
- v0.14.10 (to be released when this advisory is published)
Workarounds
Besides upgrading hyper, you can take the following options:
- Reject requests manually that contain a
Transfer-Encodingheader. - Ensure any upstream proxy rejects
Transfer-Encodingchunk sizes greater than what fits in 64-bit unsigned integers.
Credits
This issue was initially reported by Mattias Grenfeldt and Asta Olofsson.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | hyper | all versions | 0.14.10cargo update -p hyper --precise 0.14.10 |
Research 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 hyper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hyper to 0.14.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5h46-h7hh-c6x9 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-5h46-h7hh-c6x9 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-5h46-h7hh-c6x9. 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-5h46-h7hh-c6x9 in your dependencies?
O3 Security finds GHSA-5h46-h7hh-c6x9 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.