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The vulnerability arises from a discrepancy in how the `server-http` gateway and backend plugin handlers process HTTP request paths. The gateway enforces authentication only for requests whose raw path matches exactly `/api/channels` or /api/channels/. However, plugin handlers often apply canonicalization to the path—such as converting to lowercase with decodeURIComponent(pathname).toLowerCase()—before routing. This mismatch creates a bypass opportunity. An attacker can send a request to /API/channels/nostr/default/profile, where the uppercase “API” evades the gateway’s exact-match filter. The gateway sees a path that doesn’t match its strict patterns and skips authentication. The plugin handler, after lowercasing, interprets the path as `/api/channels/nostr/default/profile` and processes it as an authenticated route. Similarly, URL-encoded slashes in `/api/channels%2Fnostr%2Fdefault%2Fprofile` achieve the same effect: the gateway sees the encoded string and does not apply auth, but after decoding by the plugin, the path is treated as a valid channel request. This results in unauthorized access to plugin channel APIs that should require gateway authentication, effectively bypassing security boundaries [user input].
dailycve form:
Platform: server-http gateway
Version: affected versions unspecified
Vulnerability: authentication path bypass
Severity: moderate (CVSS 5.3)
date: October 2024
Prediction: vendor notification expected
What Undercode Say:
Analytics
The vulnerability highlights a critical class of authentication flaws rooted in inconsistent request handling between components. Path canonicalization discrepancies—whether through case transformation, URL decoding, or trailing slash normalization—create exploitable gaps. This pattern appears in numerous web frameworks and reverse proxies, often leading to severe access control breaches. The attack vector is network-based, requires no privileges, and has medium attack complexity, making it attractive for reconnaissance and limited data access.
Bash/Codes Related to the Blog
The following commands and code snippets demonstrate how to test for and understand this vulnerability:
Example curl command to test bypass using uppercase path
curl -i "http://target-server.com/API/channels/nostr/default/profile"
Example using URL-encoded slashes
curl -i "http://target-server.com/api/channels%2Fnostr%2Fdefault%2Fprofile"
Simple Python script to demonstrate canonicalization mismatch
import urllib.parse
def gateway_auth_check(raw_path):
Simulate gateway: auth only if exact match
if raw_path == "/api/channels" or raw_path.startswith("/api/channels/"):
return "Auth Required"
return "Auth Skipped"
def plugin_route_handler(raw_path):
Simulate plugin: canonicalizes input
canonical = urllib.parse.unquote(raw_path).lower()
if canonical.startswith("/api/channels/"):
return f"Plugin processing: {canonical}"
return "404 Not Found"
Test cases
test_paths = [
"/api/channels/nostr/default/profile",
"/API/channels/nostr/default/profile",
"/api/channels%2Fnostr%2Fdefault%2Fprofile"
]
for path in test_paths:
print(f"Path: {path}")
print(f" Gateway: {gateway_auth_check(path)}")
print(f" Plugin: {plugin_route_handler(path)}")
print("-" 40)
How Exploit:
An attacker crafts HTTP requests with non-canonical paths that evade the gateway’s authentication filter. Two primary methods:
1. Case manipulation: Changing `/api` to `/API` bypasses case-sensitive exact matching on the gateway.
2. URL encoding: Replacing slashes with `%2F` keeps the gateway from recognizing the path as matching /api/channels/, while the plugin decodes it back to slashes for routing.
The request reaches the plugin handler without prior authentication, and the handler processes it as if it were a legitimate authenticated request, exposing backend channel APIs.
Protection from this CVE:
- Normalize paths at the gateway: Apply the same canonicalization (lowercasing, URL decoding, trailing slash handling) before authentication checks, not after.
- Use a single, consistent routing mechanism: Both authentication and routing should operate on the same normalized request representation.
- Implement defense in depth: Apply authentication at multiple layers, including at the plugin handler itself if it exposes sensitive endpoints.
- Regular expression-based matching: Use patterns that are case-insensitive and decode-aware, e.g., `(?i)^/api/channels(/.)?$` with prior URL decoding.
Impact:
Unauthorized users can bypass authentication boundaries and access plugin channel HTTP routes intended to be protected. This leads to potential information disclosure (CVSS:C/L) and limited data modification (CVSS:I/L), as attackers may retrieve or alter data exposed through these channels. The vulnerability does not enable direct system compromise but weakens the overall security posture by allowing unauthenticated access to internal APIs.
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Sources:
Reported By: github.com
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