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GHSA-xxhq-69mf-w8cr
No affected components available
Summary
An open redirect vulnerability exists in Gogs where attacker-controlled redirect_to parameters can bypass validation, allowing redirection to arbitrary external sites.
Details
All redirects in Gogs that are validated via the IsSameSite function are vulnerable:
func IsSameSite(url string) bool {
return len(url) >= 2 && url[0] == '/' && url[1] != '/' && url[1] != '\\'
}
The function only inspects the first two characters of the URL string. This check fails to account for directory traversal sequences followed by backslashes. For example:
/a/../\example.com
The IsSameSite function checks the input supplied to the redirect_to query parameter value /a/../\example.com and considers it valid.
Because web browsers normalize backslashes \ to forward slashes /, the normalized URL becomes //example.com.
The normalized URL becomes:
//example.com
Resulting in a cross-origin redirect.
This affects all endpoints using the redirect_to query parameter, including login and other post-action flows.
PoC
- An attacker can provide a user with a link to login to Gogs with a
redirect_toquery parameter that redirects a user to a site the attacker wants them to visit:
http://192.168.236.132:3000/user/login?redirect_to=/a/../\example.com
- After the user successfully logs in, they would be redirected to the site an attacker wants them to visit:
Impact
- Phishing: Attackers can use trusted domain links to redirect victims to credential-harvesting pages
- OAuth/SSO Token Theft: In authentication flows, authorization codes or tokens may leak via redirect
- Referer Leakage: Sensitive URL parameters may be exposed to attacker domains via the Referer header
- Cache Poisoning: In deployments with shared caches, malicious redirects may be cached and served to other users
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 impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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