# CVE-2026-67868: Systerel S2OPC heap-based buffer overflow in EventFilter handling

Source: https://junglewise.ai/threats/cve-2026-67868-systerel-s2opc-heap-based-buffer-overflow-in-eventfilter-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-17. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-67868 · Severity: critical · CVSS 9.8 · Published 2026-08-17

S2OPC is an OPC UA (industrial automation protocol) server toolkit. A remote attacker can send a specially crafted OPC UA request to crash the server or potentially execute arbitrary code by exploiting a memory corruption flaw in the event filter validation logic. This can disrupt manufacturing operations or process control systems that rely on OPC UA connectivity.

Technologies: [Systerel S2OPC](https://junglewise.ai/threats/technologies/s2opc). Vendors: [Systerel](https://junglewise.ai/threats/vendors/systerel).

## Quick answers

**Is CVE-2026-67868 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-67868 being exploited in the wild.

**How severe is CVE-2026-67868?** Critical severity, with a CVSS score of 9.8, published 17 August 2026.

**Which products and versions are affected?** Systerel S2OPC 1.7.3.

**Is there a fix for CVE-2026-67868?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-67868 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-67868?** Check whether you run Systerel S2OPC at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-based out-of-bounds write vulnerability exists in S2OPC 1.7.3's server-side EventFilter validation during CreateMonitoredItems processing. The flaw occurs in the WhereClause result handling: when processing an EventFilter with multiple empty ContentFilterElements, the code allocates a zero-length OperandStatusCodes array for the first element but leaves a non-Good status for the second element due to early return, then unconditionally writes to OperandStatusCodes[0], causing a heap buffer overflow. The vulnerability is reachable remotely via crafted OPC UA network requests without prior authentication. An attacker can crash the server (denial of service) or potentially achieve remote code execution. A patch is available in newer S2OPC versions.

## Affected products

- Systerel S2OPC 1.7.3

## Timeline

- 2026-08-17: disclosed
- other: Reported in GitHub issue as server-side heap-buffer-overflow in EventFilter WhereClause handling

## References

- [https://github.com/gff-cw/information/issues/16](https://github.com/gff-cw/information/issues/16)
- [https://github.com/systerel/S2OPC/blob/b4c5c7d63cd69698461d514b905a7c92b3c377c4/src/ClientServer/services/b2c/monitored_item_event_filter_treatment_bs.c](https://github.com/systerel/S2OPC/blob/b4c5c7d63cd69698461d514b905a7c92b3c377c4/src/ClientServer/services/b2c/monitored_item_event_filter_treatment_bs.c)

## Related threats

- [S2OPC null pointer dereference in notification message allocation](https://junglewise.ai/threats/cve-2026-90782-s2opc-null-pointer-dereference-in-notification-message-allocation)
- [Systerel S2OPC use-after-free in monitored item event filter](https://junglewise.ai/threats/cve-2026-82619-systerel-s2opc-use-after-free-in-monitored-item-event-filter)
- [Systerel S2OPC out-of-bounds read in string array range writing](https://junglewise.ai/threats/cve-2026-82618-systerel-s2opc-out-of-bounds-read-in-string-array-range-writing)
- [Systerel S2OPC out-of-bounds read in AddNodes Service](https://junglewise.ai/threats/cve-2026-78049-systerel-s2opc-out-of-bounds-read-in-addnodes-service)
- [Systerel S2OPC out-of-bounds read in DeleteMonitoredItemsResponse handler](https://junglewise.ai/threats/cve-2026-18790-systerel-s2opc-out-of-bounds-read-in-deletemonitoreditemsresponse)