CVE-2026-63177 cisagov CVE debrief

Who should care

Defenders responsible for Malcolm network traffic analysis tool suite deployments should assess exposure and apply the patch to prevent potential unauthorized access. This includes reviewing and updating role-based access control configurations, monitoring for suspicious activity, and implementing additional logging and monitoring measures. Security teams and vulnerability management teams should prioritize verifying and applying the patch to prevent data

Why it matters

CVE-2026-63177 is a high-severity vulnerability in the Malcolm network traffic analysis tool suite that allows an authenticated low-privilege user to bypass role-based access control and access restricted backends. Defenders should prioritize verifying and applying the patch to prevent potential unauthorized access.

• Potential unauthorized access to restricted backends
• Bypass of role-based access control
• Increased risk of data breaches or system compromise
• Need for verification and patch application

Technical summary

The vulnerability is caused by the role-based access control in the Nginx OpenResty Lua layer evaluating the raw, unnormalized `ngx.var.request_uri`, while Nginx routes requests using the normalized path. This allows an authenticated low-privilege user to bypass access control and access restricted backends. The issue arises from the discrepancy between the Lua layer's evaluation of the raw request URI and Nginx's routing based on the normalized path. An attacker can exploit this by prepending a traversal segment to the request URI, potentially leading to unauthorized access and data breaches.

Defensive priority

Defenders should prioritize verifying and applying the patch to prevent potential unauthorized access.

Recommended defensive actions

• Verify and apply the patch to Malcolm version 26.07.0 or later
• Review and update role-based access control configurations to prevent similar bypasses
• Monitor for suspicious activity and implement additional logging and monitoring measures
• 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 the role-based access control in the Nginx OpenResty Lua layer evaluating the raw, unnormalized `ngx.var.request_uri`, while Nginx routes requests using the normalized path. This allows an authenticated low-privilege user to bypass access control and access restricted backends.

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.