GHSA-5rvq-cxj2-64vf
HIGHGHSA-5rvq-cxj2-64vf is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in python-multipart. O3 Security confirms whether GHSA-5rvq-cxj2-64vf is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
python-multipart: Quadratic-time querystring parsing with semicolon separators causes CPU denial of service
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-5rvq-cxj2-64vf.
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-5rvq-cxj2-64vf 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 0 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
python-multipartReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
When parsing application/x-www-form-urlencoded bodies, QuerystringParser located the field separator with a two step lookup: it first scanned the entire remaining buffer for &, and only when no & existed anywhere ahead did it fall back to scanning for ;. For a body that uses ; as the separator and contains no &, every field iteration performed a full failed & scan over the entire remaining buffer before locating the nearby ;. With N semicolon separated fields in a chunk of size B, this yields O(B^2) byte comparisons per chunk.
An attacker can submit a small crafted body of the form a;a;a;... and cause the parser to spend seconds of CPU per request. A handful of concurrent requests can exhaust worker processes.
Details
In python_multipart/multipart.py, both the FIELD_NAME and FIELD_DATA states located the next separator like this:
sep_pos = data.find(b"&", i)
if sep_pos == -1:
sep_pos = data.find(b";", i)
data.find(b"&", i) scans from i to the end of the buffer and returns -1 only when there is no & anywhere in the remainder. For a ; separated body with no &, this failed full buffer scan repeats once per field, making parsing quadratic in the body length.
For example, a 1 MiB url encoded body consisting of a; repeated ~500,000 times, submitted with Content-Type: application/x-www-form-urlencoded, causes the parser to perform on the order of 10^11 byte comparisons, consuming several seconds of CPU for a single request. Cost scales quadratically with chunk size.
The parser is reachable through the public QuerystringParser class and through the high level FormParser, create_form_parser, and parse_form APIs for url encoded bodies. It is also the parser Starlette and FastAPI use for application/x-www-form-urlencoded request bodies via request.form().
Impact
Uncontrolled CPU consumption (denial of service). Parsing is synchronous, so a single small crafted form body occupies the handling worker for seconds, blocking any other work on that worker until parsing finishes. Sustained concurrent requests keep workers continuously busy, degrading or denying service.
Mitigation
Upgrade to python-multipart 0.0.30 or later, which treats only & as a field separator (per the WHATWG URL standard) using a single bounded scan, making parsing linear in the body length.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | python-multipart | all versions | 0.0.30 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for python-multipart. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update python-multipart to 0.0.30 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5rvq-cxj2-64vf 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 pinpoints whether GHSA-5rvq-cxj2-64vf is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-5rvq-cxj2-64vf. 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-5rvq-cxj2-64vf in your dependencies?
O3 detects GHSA-5rvq-cxj2-64vf across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.