GHSA-3h23-rrpc-3p87 is a high-severity (CVSS 8.2) CWE-284 vulnerability in pkg.jsn.cam/caddy-defender. O3 Security confirms whether GHSA-3h23-rrpc-3p87 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Caddy Defender trusted proxy client IP bypass
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-3h23-rrpc-3p87.
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-3h23-rrpc-3p87 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
pkg.jsn.cam/caddy-defenderReal-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
Caddy Defender used r.RemoteAddr when evaluating whether a request should be blocked. RemoteAddr is the address of the immediate peer connected to Caddy.
In deployments where Caddy is behind a trusted proxy, CDN, or load balancer, the immediate peer is usually the proxy, not the original client. Caddy resolves the original client address into its client_ip request variable after applying the configured trusted_proxies policy, but Defender did not use that value.
As a result, clients from blocked IP ranges could bypass Defender when accessing Caddy through a trusted proxy whose own IP address was not blocked. This affects deployments that use Defender behind trusted proxies and expect it to enforce blocking based on the real client IP.
Patches
The issue is fixed by making Defender prefer Caddys resolved client_ip request variable when it is available. Defender falls back to RemoteAddr only when Caddy has not provided a resolved client IP.
Users should upgrade to v0.10.1 or later.
Workarounds
There is no complete workaround in affected Defender versions for deployments that rely on Caddys trusted proxy client IP resolution.
Until upgrading, affected users should enforce equivalent IP blocking at the trusted proxy, CDN, load balancer, firewall, or other edge layer before traffic reaches Caddy.
Deployments where Caddy receives traffic directly from clients, without an intermediate trusted proxy, are not affected by this bypass.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | pkg.jsn.cam/caddy-defender | all versions | 0.10.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pkg.jsn.cam/caddy-defender. 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 pkg.jsn.cam/caddy-defender to 0.10.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3h23-rrpc-3p87 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-3h23-rrpc-3p87 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-3h23-rrpc-3p87. 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-3h23-rrpc-3p87 in your dependencies?
O3 detects GHSA-3h23-rrpc-3p87 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.