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Vulnerabilities

Vulnerability · CVE-2026-21870

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services.

Published Feb 13, 2026 · catalog updated Feb 13, 2026 · BACnet Protocol Stack library

Last checked Nov 3, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21870. EPSS is 0.28%. Act only if a listed version of BACnet Protocol Stack library is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (BACnet Protocol Stack library).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.28%
Remediation
Advisory link
Affected products
vendor bacnet-stack bacnet-stack ≤ 1.4.2

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor bacnet-stack bacnet-stack ≤ 1.4.2≤ 1.4.2

How to fix CVE-2026-21870

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-21870. EPSS is 0.28%. Act only if a listed version of BACnet Protocol Stack library is installed.

Which versions are affected?

Compare what you have installed with bacnet-stack bacnet-stack ≤ 1.4.2 ≤ 1.4.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.28%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 13, 2026 · EUVD

    Detected

    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

  2. Feb 13, 2026 · EUVD

    Updated

    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

Sources

  • FIRST EPSSExploitation probabilityCVE-2026-21870

    30-day exploitation probability 0.28%

    first.org
  • EUVDVulnerability recordEUVD-2026-5920

    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 st

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 3, 2026
  • EUVDNov 3, 2026