CVE-2026-45694 librenms CVE debrief

Who should care

Defenders responsible for LibreNMS installations, especially those with authenticated users who may be lured into following crafted links, should assess exposure and prioritize patching or mitigation.

Why it matters

CVE-2026-45694 is a reflected cross-site scripting vulnerability in LibreNMS that can be exploited through user-supplied instance and vmid GET parameters, allowing an attacker to execute script in an authenticated user's session.

• Theft of session data is possible if an attacker can lure an authenticated user into following a crafted link.
• An attacker can execute script in an authenticated user's session, potentially leading to unauthorized actions.
• Defenders should verify if their systems are vulnerable and prioritize patching or mitigation.

Technical summary

The vulnerability exists in the Proxmox application view of LibreNMS versions up to and including 26.4.0. User-supplied instance and vmid GET parameters are reflected into the page title without adequate encoding, allowing an attacker to execute script in an authenticated user's session. This can enable actions such as theft of session data. The issue is fixed in version 26.5.0. Defenders should prioritize patching or mitigating this vulnerability, especially in systems where authenticated users may be lured into following crafted links.

Defensive priority

Defenders should prioritize patching or mitigating this vulnerability, especially in systems where authenticated users may be lured into following crafted links.

Recommended defensive actions

• Patch or upgrade to LibreNMS version 26.5.0 or later
• Implement input validation and output encoding for user-supplied data
• Monitor for suspicious activity and implement session management best practices
• 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 CVE record and NVD entry provide details on the vulnerability, its impact, and the fix. However, additional information on potential exploitation or affected systems is limited. Defenders should verify if their systems are vulnerable by checking for LibreNMS versions up to and including 26.4.0 and prioritize patching or mitigation. They should also review system logs for suspicious activity and implement session management best practices.

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.