CVE-2026-52846
MEDIUMCVE-2026-52846 is a medium-severity (CVSS 4.2) CWE-116 vulnerability in github.com/caddyserver/caddy/v2. O3 Security confirms whether CVE-2026-52846 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Caddy: stripHTML template function bypass
Blast Radius
github.com/caddyserver/caddy/v2🐹github.com/caddyserver/caddyReal-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
Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, Caddy’s stripHTML template function cannot reliably remove all HTML tags from input strings. Certain malformed HTML, such as <<>img src=x onerror=alert()>, can bypass the tag-stripping logic, potentially leaving dangerous content in the output if it is later rendered as HTML. This may allow client-side XSS in cases where untrusted strings are rendered unsafely. This vulnerability is fixed in 2.11.4.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/caddyserver/caddy/v2 | all versions | 2.11.4 |
| 🐹Go | github.com/caddyserver/caddy | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/caddyserver/caddy/v2. 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 github.com/caddyserver/caddy/v2 to 2.11.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-52846 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 CVE-2026-52846 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 CVE-2026-52846. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-52846 in your dependencies?
O3 detects CVE-2026-52846 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.