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GHSA-4fxq-2x3x-6xqx

MediumCVSS 6.1 / 10
Published Apr 16, 2026·Last modified May 5, 2026
Affected Components(0)

No affected components available

Description

Summary The 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.

  • Attack Vector: Network — the attack is delivered as a crafted URL over the internet.
  • Attack Complexity: Low — no race conditions or special environment prerequisites.
  • Privileges Required: None — the attacker needs no account on the zrok instance.
  • User Interaction: Required — the victim must click the crafted link and complete the GitHub OAuth flow.
  • Scope: Changed — the injected script executes in the OAuth server's origin, not the victim's share origin.
  • 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.
  • Integrity Impact: Low — the script can initiate new OAuth flows or submit forms on behalf of the victim in the OAuth server origin.
  • Availability Impact: None.

Affected Components

  • endpoints/proxyUi/template.go — init() / WriteTemplate (lines 8, 18, 99) — text/template used for HTML rendering
  • endpoints/proxyUi/template.html — line 119 — {{ .Error }} in HTML without escaping
  • endpoints/publicProxy/providerGithub.go — login callback closure (lines 93, 128, 130)
  • endpoints/dynamicProxy/providerGithub.go — loginHandler() (lines 110, 146, 148)
Risk Scores
Base Score
6.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
5.6

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.21%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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