# CVE-2026-100403: BACnet Stack: BACnet/SC hub grows its WebSocket reassembly buffer without limit, so a peer can exhaust its memory

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to versions 1.4.6, 1.5.2, and 1.6.1, the BACnet/SC hub's Linux WebSocket server reassembles fragmented WebSocket messages into a per-connection fragment_buffer. It grows that buffer with realloc() on every non-final frame, with no upper bound. A peer that streams binary continuation fragments and never sets FIN keeps the hub reallocating until the box runs out of memory or the process is OOM-killed. The buffer starts at the maximum legal BVLC-SC NPDU size, but nothing after that ties its growth back to that limit. This issue has been patched in versions 1.4.6, 1.5.2, 1.6.1, and 1.7.0.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- bacnet-stack / bacnet-stack: < 1.4.6 (affected); >= 1.5.0, < 1.5.2 (affected); >= 1.6.0, < 1.6.1 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-400

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-4vgv-v5ph-rmxr (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/bacnet-stack/bacnet-stack/pull/1433 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-100403; retrieved 2026-11-13; source updated 2026-11-13

Revision: b4612703855809523bde4e181653f8ab62fc95ed35a241f20bc91dfe4022dbd9

Canonical: https://y2.dev/cve/CVE-2026-100403

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