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CVE-2026-21870

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]
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:98b2f79b5073a35473f8b3c5de6b1dc45208c843134351e4ad44641bc5ece551
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
0

Affected products and versions

1 source assertion
{"product":"bacnet-stack","vendor":"bacnet-stack","versions":[{"status":"affected","version":"<= 1.4.2"},{"status":"affected","version":">= 1.5.0.rc1, <= 1.5.0.rc2"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:fdcd3bbd1f1059a79f70c614fb92bd52d0054cfb71f9409f57fd7187f268e42d · sha256:79c3125994f7c2e0… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":5.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:fdcd3bbd1f1059a79f70c614fb92bd52d0054cfb71f9409f57fd7187f268e42d · sha256:79c3125994f7c2e0… · /containers/cna/metrics/0/cvssV3_1

CWE assertions

1 source assertion
{"cweId":"CWE-193","description":"CWE-193: Off-by-one Error","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:fdcd3bbd1f1059a79f70c614fb92bd52d0054cfb71f9409f57fd7187f268e42d · sha256:79c3125994f7c2e0… · /containers/cna/problemTypes/0/descriptions/0

Source references

3 source assertions
{"name":"https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465","tags":["x_refsource_MISC"],"url":"https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:fdcd3bbd1f1059a79f70c614fb92bd52d0054cfb71f9409f57fd7187f268e42d · sha256:79c3125994f7c2e0… · /containers/cna/references/2
{"name":"https://github.com/bacnet-stack/bacnet-stack/pull/1196","tags":["x_refsource_MISC"],"url":"https://github.com/bacnet-stack/bacnet-stack/pull/1196"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:fdcd3bbd1f1059a79f70c614fb92bd52d0054cfb71f9409f57fd7187f268e42d · sha256:79c3125994f7c2e0… · /containers/cna/references/1
{"name":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx","tags":["x_refsource_CONFIRM"],"url":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:fdcd3bbd1f1059a79f70c614fb92bd52d0054cfb71f9409f57fd7187f268e42d · sha256:79c3125994f7c2e0… · /containers/cna/references/0

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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