GHSA-c5c4-8r6x-56w3 — v7
MEDIUMGHSA-c5c4-8r6x-56w3 is a medium-severity (CVSS 6.8) CWE-863 vulnerability in github.com/oauth2-proxy/oauth2-proxy/v7. A fix is available for github.com/oauth2-proxy/oauth2-proxy/v7 — see the affected versions and patch details below.
OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-c5c4-8r6x-56w3.
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-c5c4-8r6x-56w3 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/oauth2-proxy/oauth2-proxy/v7Real-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
Impact
An authorization bypass exists in OAuth2 Proxy as part of the email_domain enforcement option. An attacker may be able to authenticate with an email claim such as [email protected]@company.com and satisfy an allowed domain check for company.com, even though the claim is not a valid email address.
The issue ONLY affects deployments that rely on email_domain restrictions and accept email claim values from identity providers or claim mappings that do not strictly enforce normal email syntax. The practical risk ONLY exists in self-hosted or custom OIDC environments and federated setups where unexpected claim values can reach oauth2-proxy. Standard hosted providers that enforce valid email formatting ARE NOT effected.
Patches
Users should upgrade to v7.15.2 or later once available.
Workarounds
The most effective workaround is to ensure the configured identity provider cannot emit malformed or attacker-controlled email claim values.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/oauth2-proxy/oauth2-proxy/v7 | all versions | 7.15.2go get github.com/oauth2-proxy/oauth2-proxy/v7@v7.15.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/oauth2-proxy/oauth2-proxy/v7, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/oauth2-proxy/oauth2-proxy/v7 to 7.15.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c5c4-8r6x-56w3 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-c5c4-8r6x-56w3 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-c5c4-8r6x-56w3. 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-c5c4-8r6x-56w3 in your dependencies?
O3 Security finds GHSA-c5c4-8r6x-56w3 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.