CVE-2026-26264

Summary

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.5.0rc4 and 1.4.3rc2, a malformed WriteProperty request can trigger a length underflow in the BACnet stack, leading to an out‑of‑bounds read and a crash (DoS). The issue is in wp.c within wp_decode_service_request. When decoding the optional priority context tag, the code passes apdu_len - apdu_size to bacnet_unsigned_context_decode without validating that apdu_size <= apdu_len. If a truncated APDU reaches this path, apdu_len - apdu_size underflows, resulting in a large size being used for decoding and an out‑of‑bounds read. This vulnerability is fixed in 1.5.0rc4 and 1.4.3rc2.

Affected Software

VendorProductVersion RangeStatus
bacnet-stackbacnet-stack>= 1.5.0rc1, < 1.5.0rc4affected
bacnet-stackbacnet-stack< 1.4.3rc2affected

Weaknesses

  • CWE-125: CWE-125: Out-of-bounds Read

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: yes
    • Technical Impact: partial

References