{"id":"GHSA-4fxq-2x3x-6xqx","summary":"zrok: Reflected XSS in GitHub OAuth callback via unsanitized refreshInterval error rendering","details":"**Summary**\nThe proxyUi template engine uses Go's text/template (which performs no HTML escaping) instead of html/template. The GitHub OAuth callback handlers in both publicProxy and dynamicProxy embed the attacker-controlled refreshInterval query parameter verbatim into an error message when time.ParseDuration fails, and render that error unescaped into HTML. An attacker can deliver a crafted login URL to a victim; after the victim completes the GitHub OAuth flow, the callback page executes arbitrary JavaScript in the OAuth server's origin.\n\n- Attack Vector: Network — the attack is delivered as a crafted URL over the internet.\n- Attack Complexity: Low — no race conditions or special environment prerequisites.\n- Privileges Required: None — the attacker needs no account on the zrok instance.\n- User Interaction: Required — the victim must click the crafted link and complete the GitHub OAuth flow.\n- Scope: Changed — the injected script executes in the OAuth server's origin, not the victim's share origin.\n- Confidentiality Impact: Low — the script runs in the OAuth server origin after a failed flow; no session cookie is set at this point, limiting what can be exfiltrated to what is visible in the DOM and what can be requested from the OAuth server.\n- Integrity Impact: Low — the script can initiate new OAuth flows or submit forms on behalf of the victim in the OAuth server origin.\n- Availability Impact: None.\n\n**Affected Components**\n\n- endpoints/proxyUi/template.go — init() / WriteTemplate (lines 8, 18, 99) — text/template used for HTML rendering\n- endpoints/proxyUi/template.html — line 119 — {{ .Error }} in HTML without escaping\n- endpoints/publicProxy/providerGithub.go — login callback closure (lines 93, 128, 130)\n- endpoints/dynamicProxy/providerGithub.go — loginHandler() (lines 110, 146, 148)","aliases":["CVE-2026-40302","GO-2026-5118"],"modified":"2026-06-25T18:56:29.323523594Z","published":"2026-04-16T21:08:55Z","database_specific":{"github_reviewed_at":"2026-04-16T21:08:55Z","nvd_published_at":"2026-04-17T21:16:34Z","cwe_ids":["CWE-116","CWE-79"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/openziti/zrok/security/advisories/GHSA-4fxq-2x3x-6xqx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40302"},{"type":"PACKAGE","url":"https://github.com/openziti/zrok"},{"type":"WEB","url":"https://github.com/openziti/zrok/releases/tag/v2.0.1"}],"affected":[{"package":{"name":"github.com/openziti/zrok","ecosystem":"Go","purl":"pkg:golang/github.com/openziti/zrok"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"last_affected":"1.1.11"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-4fxq-2x3x-6xqx/GHSA-4fxq-2x3x-6xqx.json"}},{"package":{"name":"github.com/openziti/zrok/v2","ecosystem":"Go","purl":"pkg:golang/github.com/openziti/zrok/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.0.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-4fxq-2x3x-6xqx/GHSA-4fxq-2x3x-6xqx.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"}]}