CVE-2026-96748 MongoDB CVE debrief

Who should care

Defenders responsible for maintaining MongoDB connections and applications that use PyMongo should assess exposure and prioritize verification and remediation. This includes reviewing applications that interpolate untrusted input into MongoDB connection strings and verifying PyMongo versions. Additionally, defenders should implement security measures to prevent unauthorized access and monitor for potential credential exposure or unauthorized operations.

Why it matters

CVE-2026-96748 is a vulnerability in PyMongo's connection string parsing that could allow an attacker to inject a malicious host into the client's seed list, potentially leading to credential exposure or unauthorized operations. Defenders should prioritize verifying and updating PyMongo, especially in applications using untrusted input in MongoDB connection strings.

• Potential credential exposure due to unauthorized host addition
• Possible unauthorized operations through malicious host routing
• Need for verification of affected versions and remediation through updates
• Importance of secure connection string handling practices

Technical summary

PyMongo's connection string parsing vulnerability allows an attacker to inject a malicious host into the client's seed list by percent-encoding delimiters. This issue affects applications that interpolate untrusted input into a MongoDB connection string. The vulnerability arises from PyMongo's percent-decoding of the entire host section of a connection string before splitting it into individual host:port entries. This allows an attacker to inject an additional host and port into the client's seed list. Defenders should prioritize verifying and updating PyMongo to version 4.18.2 or later, especially in applications that use untrusted input in MongoDB connection strings. The fix involves moving percent-decoding

Defensive priority

Defenders should prioritize verifying and updating PyMongo to version 4.18.2 or later, especially in applications that use untrusted input in MongoDB connection strings.

Recommended defensive actions

• Verify and update PyMongo to version 4.18.2 or later
• Review applications that use untrusted input in MongoDB connection strings
• Implement additional security measures to prevent unauthorized access
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by PyMongo's percent-decoding of the entire host section of a connection string before splitting it into individual host:port entries. This allows an attacker to inject an additional host and port into the client's seed list.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.