bacnet-stack up to 1.4.2/1.5.0.rc2 tokenizer.c tokenizer_string off-by-one

CVSS Meta Temp Score
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CTI Interest Score
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4.1$0-$5k0.00

Summaryinfo

A vulnerability identified as problematic has been detected in bacnet-stack up to 1.4.2/1.5.0.rc2. The impacted element is the function tokenizer_string of the file src/bacnet/basic/program/ubasic/tokenizer.c. The manipulation leads to off-by-one. This vulnerability is referenced as CVE-2026-21870. The attack can only be performed from a local environment. No exploit is available. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in bacnet-stack up to 1.4.2/1.5.0.rc2. This issue affects the function tokenizer_string of the file src/bacnet/basic/program/ubasic/tokenizer.c. The manipulation with an unknown input leads to a off-by-one vulnerability. Using CWE to declare the problem leads to CWE-193. A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. Impacted is availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-21870 since 01/05/2026. The exploitation is known to be easy. Attacking locally is a requirement. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

Applying the patch 4e1176394a5ae50d2fd0b5790d9bff806dc08465 is able to eliminate this problem. The bugfix is ready for download at github.com.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.1
VulDB Meta Temp Score: 4.1

VulDB Base Score: 2.8
VulDB Temp Score: 2.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.5
CNA Vector (GitHub_M): 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Off-by-one
CWE: CWE-193 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Patch: 4e1176394a5ae50d2fd0b5790d9bff806dc08465

Timelineinfo

01/05/2026 CVE reserved
02/13/2026 +39 days Advisory disclosed
02/13/2026 +0 days VulDB entry created
02/13/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-pc83-wp6w-93mx
Status: Confirmed

CVE: CVE-2026-21870 (🔒)
GCVE (CVE): GCVE-0-2026-21870
GCVE (VulDB): GCVE-100-345935

Entryinfo

Created: 02/13/2026 20:31
Changes: 02/13/2026 20:31 (65)
Complete: 🔍
Cache ID: 216::103

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