CVE-2026-21870
The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string
Description
BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow.
INFO
Published Date :
Feb. 13, 2026, 6:16 p.m.
Last Modified :
Feb. 13, 2026, 6:16 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-21870
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE |
Solution
- Update to a patched version of the BACnet Protocol Stack library.
- Review and correct the tokenizer_string function's null termination handling.
- Ensure string literals do not exceed buffer limits.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-21870.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-21870 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-21870
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-21870 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-21870 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Feb. 13, 2026
Action Type Old Value New Value Added Description BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow. Added CVSS V3.1 AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Added CWE CWE-193 Added Reference https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465 Added Reference https://github.com/bacnet-stack/bacnet-stack/pull/1196 Added Reference https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx