FKIE_CVE-2026-21870

Vulnerability from fkie_nvd - Published: 2026-02-13 18:16 - Updated: 2026-02-18 18:49
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Summary
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.
References
security-advisories@github.comhttps://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465Patch
security-advisories@github.comhttps://github.com/bacnet-stack/bacnet-stack/pull/1196Patch
security-advisories@github.comhttps://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mxVendor Advisory, Exploit
Impacted products
Vendor Product Version
bacnetstack bacnet_stack *
bacnetstack bacnet_stack 1.5.0
bacnetstack bacnet_stack 1.5.0
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{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "3BF2BFCC-54CE-412E-947A-B5C834161829",
              "versionEndIncluding": "1.4.2",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc1:*:*:*:*:*:*",
              "matchCriteriaId": "2B47182E-6B7F-4C53-904A-EB37C9C0A439",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc2:*:*:*:*:*:*",
              "matchCriteriaId": "CF491863-1A31-4A23-A6AC-DF7545FCAA48",
              "vulnerable": true
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          "negate": false,
          "operator": "OR"
        }
      ]
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    }
  ],
  "id": "CVE-2026-21870",
  "lastModified": "2026-02-18T18:49:07.307",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "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"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
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  "published": "2026-02-13T18:16:19.783",
  "references": [
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      "source": "security-advisories@github.com",
      "tags": [
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      "url": "https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465"
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      "source": "security-advisories@github.com",
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    },
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      "source": "security-advisories@github.com",
      "tags": [
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      "url": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx"
    }
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  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
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          "lang": "en",
          "value": "CWE-193"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}


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