Detect MongoDB Improper Handling of Length Parameter Inconsistency (CVE-2025-14847) in Splunk
Detects exploitation attempts targeting CVE-2025-14847, an improper handling of length parameter inconsistency vulnerability (CWE-130) in MongoDB and MongoDB Server. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild. Attackers may craft malformed requests with inconsistent length parameters to cause unexpected server behavior, potentially leading to denial of service, data corruption, or unauthorized access.
MITRE ATT&CK
- Tactic
- Initial Access Impact
SPL Detection Query
index=* sourcetype IN ("mongod", "mongodb", "mongodb:diagnostic", "syslog") earliest=-24h
| where match(_raw, "(?i)(length.*inconsisten|param.*mismatch|bson.*invalid|assertion.*failed|malformed.*request)")
OR (match(host, "(?i)mongo") AND match(_raw, "(?i)(exception|error|assertion)"))
| eval risk_score=case(
match(_raw, "(?i)(assertion|malformed)"), 80,
match(_raw, "(?i)(length.*inconsisten|bson.*invalid)"), 90,
true(), 50
)
| stats count as event_count, max(risk_score) as max_risk, values(_raw) as raw_events, dc(host) as unique_hosts by host, sourcetype
| where event_count > 1 OR max_risk >= 80
| sort - max_riskSearches MongoDB log sourcetypes for patterns consistent with CVE-2025-14847 length parameter inconsistency exploitation. Assigns risk scores and aggregates by host to surface high-confidence events.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Routine MongoDB maintenance operations generating assertion or error log entries
- BSON validation errors from legitimate client application bugs unrelated to exploitation
- MongoDB replica set elections or stepdowns producing transient error messages
- Development or QA environments running MongoDB with verbose debug logging enabled
Other platforms for CVE-2025-14847
Testing Methodology
Validate this detection against 3 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.
- Test 1Send Malformed BSON Message with Inconsistent Length to MongoDB
Expected signal: MongoDB diagnostic log should record a parse error, assertion failure, or connection reset. Network capture should show malformed wire protocol frame followed by TCP RST or server-side close.
- Test 2Fuzzing MongoDB Port with Length Boundary Payloads
Expected signal: Multiple connection events on port 27017 in rapid succession, followed by MongoDB log entries for parser errors or assertion failures for each boundary value tested.
- Test 3Verify MongoDB Version and Patch Status
Expected signal: MongoDB audit log (if enabled) records a connection and command execution from localhost. Authentication log shows anonymous or credential-less connection attempt.
Unlock Pro Content
Get the full detection package for CVE-2025-14847 including response playbook, investigation guide, and atomic red team tests.