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CVE-2026-21878— BACnet Stack Improperly Limits Pathnames to a Restricted Directory

Quick assessment

Affected
bacnet-stack bacnet-stack
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

BACnet Stack是BACnet Stack开源的一个适用于嵌入式系统、Linux、MacOS、BSD 和 Windows 的 BACnet 开源协议栈 C 库。 BACnet Stack 1.5.0.rc3之前版本存在路径遍历漏洞，该漏洞源于文件写入功能未验证用户提供的文件路径，可能导致向任意目录写入文件。

CVSS 7.5 · High EPSS 0.38% · P29
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I. Basic Information for CVE-2026-21878

Vulnerability Information
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Vulnerability Title
BACnet Stack Improperly Limits Pathnames to a Restricted Directory
Source: CVE Program / CVE List V5
Vulnerability Description
BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.5.0.rc3, a vulnerability has been discovered in BACnet Stack's file writing functionality where there is no validation of user-provided file paths, allowing attackers to write files to arbitrary directories. This affects apps/readfile/main.c and ports/posix/bacfile-posix.c. This vulnerability is fixed in 1.5.0.rc3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
BACnet Stack 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
BACnet Stack是BACnet Stack开源的一个适用于嵌入式系统、Linux、MacOS、BSD 和 Windows 的 BACnet 开源协议栈 C 库。 BACnet Stack 1.5.0.rc3之前版本存在路径遍历漏洞，该漏洞源于文件写入功能未验证用户提供的文件路径，可能导致向任意目录写入文件。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
bacnet-stack bacnet-stack < 1.5.0.rc3 -

II. Public POCs for CVE-2026-21878

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III. Intelligence Information for CVE-2026-21878

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Patches & Fixes for CVE-2026-21878 (1)

Same Patch Batch · bacnet-stack · 2026-02-13 · 3 CVEs total

CVE-2026-21870 5.5 MEDIUM The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokeniz
CVE-2026-26264 BACnet Stack WriteProperty decoding length underflow leads to OOB read and crash

IV. Related Vulnerabilities

Same product: bacnet-stack
Same vendor: bacnet-stack
Same weakness: CWE-22

V. Comments for CVE-2026-21878

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