GHSA-273q-qgh5-wrj6 nebula-mesh's web UI lacks CSRF tokens on /ui/* mutating endpoints

• Go github.com/juev/nebula-mesh: < 0.3.3 → fixed in 0.3.3

Every `/ui/*` POST / PUT / PATCH / DELETE route processes the request as soon as the session cookie validates. `SameSite=Lax` on the session cookie prevents most cross-site form submits but does not protect: • top-level form-submit navigations from third-party pages (some browsers still send Lax cookies on top-level POSTs) • same-registrable-domain attackers (sibling-subdomain XSS, subdomain takeover) • the `GET /ui/logout` route, which a third-party `` can force-trigger The admin UI signs CA certificates, mints API keys, rotates / retires / deletes CAs, disables operators, and changes server settings. CSRF here is a real privilege escalation, not just annoyance. Affected All released versions up to v0.3.2. Suggested fix Double-submit cookie: a 32-byte `crypto/rand` token in a non-HttpOnly `_csrf` cookie, echoed in either `X-CSRF-Token` (htmx) or a `_csrf` form field (HTML forms). Compared in constant time. Rotated on every privilege transition (`Login`, OIDC `StartAuthenticatedSession`, `CompleteTwoFactor`, `Logout`) so pre-auth fixation cannot survive promotion. Rejections audit-logged as `ui.csrf.rejected` with reason; response body stays opaque. `/ui/logout` becomes POST so it is no longer reachable via `` tags. Fix coordinates with the Secure-cookie advisory disclosed concurrently — the `_csrf` cookie inherits the same `Secure`-attribute derivation. Reproducer With an authenticated operator session in browser tab A, open the following minimal HTML in any other tab: ```html Click for free puppy ``` Click. The CA is deleted — the server processes the POST because the session cookie is automatically attached and there is no other check. The same trick works for force-rotate, retire, mint API keys, disable operators, etc. Alternative force-logout: `` placed on an attacker's page logs out any visiting authenticated operator. No interaction required. Notes • Multipart and JSON endpoints don't exist in the current UI surface. Future additions must rely on the header path because `r.PostFormValue` only reads `application/x-www-form-urlencoded` bodies. The middleware's package comment documents this. • The patch assumes nebula-mgmt is the sole authority on its registrable domain. A compromised sibling subdomain can still set parent-domain cookies and forge matches; SameSite=Lax does not prevent that. Documented in the patch.