CVE-2020-36564 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in github.com/justinas/nosurf. A fix is available for github.com/justinas/nosurf — see the affected versions and patch details below.
nosurf vulnerable to improper input validation
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 CVE-2020-36564.
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
github.com/justinas/nosurfReal-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
Due to improper validation of caller input, validation is silently disabled if the provided expected token is malformed, causing any user supplied token to be considered valid.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/justinas/nosurf | all versions | 1.1.1go get github.com/justinas/nosurf@v1.1.1 |
Affected Products
nosurfnosurf_projectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/justinas/nosurf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/justinas/nosurf to 1.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-36564 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.
Frequently Asked Questions
Is CVE-2020-36564 in your dependencies?
Find it across Go, including transitive dependencies.