Vulnerability in BACnet Stack's File Writing Functionality Exposes Applications to Directory Traversal Attacks
CVE-2026-21878

7.5HIGH

Key Information:

Vendor

Bacnet-stack

Status
Bacnet-stack
Vendor
CVE Published:
13 February 2026

What is CVE-2026-21878?

A significant vulnerability has been identified in the BACnet Stack, an open-source protocol library utilized in embedded systems. The flaw resides within the file writing functionality, specifically in the handling of user-provided file paths, which lacks proper validation. This deficiency enables malicious actors to execute directory traversal attacks, potentially allowing them to write files to arbitrary locations within the system. This vulnerability impacts files located in apps/readfile/main.c and ports/posix/bacfile-posix.c. A fix addressing this issue has been implemented in version 1.5.0.rc3.

Affected Version(s)

bacnet-stack < 1.5.0.rc3

References

https://github.com/bacnet-stack/bacnet-stack/security/adv...
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https://github.com/bacnet-stack/bacnet-stack/commit/c5dc0...
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CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.