{"answers":{"affected":"It affects 1 product.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40279 exists.","fix":"No fix has been published for CVE-2026-40279 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-40279 is a low-severity vulnerability in bacnet-stack, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-40279 and fix it if it is affected.\n\nWhat it is: CVE-2026-40279 is a low-severity vulnerability in bacnet-stack, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40279 exists.\n\nAffected product: bacnet-stack. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-40279/ (Markdown: https://insights.sbomify.com/CVE-2026-40279/index.md)","id":"CVE-2026-40279","markdown":"https://insights.sbomify.com/CVE-2026-40279/index.md","name":"CVE-2026-40279","record":{"aliases":["GHSA-326g-j95f-gmxv"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"BACnet protocol stack","requires_auth":"none","summary":"Undefined behavior from signed left shifts in BACnet Stack can cause crashes or unpredictable behavior when processing specific BACnet data.","user_interaction":"not_required","vuln_class":"integer_overflow"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"bacnet_stack","vendor":"bacnetstack"}],"cvss":{"score":3.7,"severity":"low","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"},"cwes":[{"id":"CWE-758","name":"Reliance on Undefined, Unspecified, or Implementation-Defined Behavior"}],"description":"BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, decode_signed32() in src/bacnet/bacint.c reconstructs a 32-bit signed integer from four APDU bytes using signed left shifts. When any of the four bytes has bit 7 set (value ≥ 0x80), the left-shift operation overflows a signed int32_t, which is undefined behavior per the C standard. This is flagged thousands of times per minute by UndefinedBehaviorSanitizer on any BACnet input containing signed-integer property values with high-bit-set bytes. This vulnerability is fixed in 1.4.3.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"weaponised"},"has_fix":false,"headline":"BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`","id":"CVE-2026-40279","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"integer_overflow","year":"2026"},"n_packages":0,"n_references":1,"next":{"headline":"Gotenberg SSRF via case-insensitive URL scheme bypass in webhook and downloadFrom deny-lists","id":"CVE-2026-40280"},"packages":[],"prev":{"headline":"Vulnerability in the QNX libtraceparser Impacts QNX Software Development Platform","id":"CVE-2026-40272"},"products":["bacnet-stack"],"published":"2026-04-21","related":[{"cvss_score":9.1,"headline":"Memory corruption in n/a","id":"CVE-2023-51773","kev_date_added":null,"published":"2023-12-25"},{"cvss_score":8.7,"headline":"BACnet Stack: Out-of-Bounds Read in WritePropertyMultiple Decoder via Deprecated Tag Parser","id":"CVE-2026-41475","kev_date_added":null,"published":"2026-04-24"},{"cvss_score":8.7,"headline":"BACnet Stack: Off-by-One Out-of-Bounds Read in ReadPropertyMultiple Object ID Decoder","id":"CVE-2026-41502","kev_date_added":null,"published":"2026-04-24"},{"cvss_score":8.7,"headline":"BACnet Stack: Out-of-Bounds Read in ReadPropertyMultiple Property Decoder via Deprecated Tag Parser","id":"CVE-2026-41503","kev_date_added":null,"published":"2026-04-24"},{"cvss_score":7.8,"headline":"BACnet Stack WriteProperty decoding length underflow leads to OOB read and crash","id":"CVE-2026-26264","kev_date_added":null,"published":"2026-02-13"},{"cvss_score":7.5,"headline":"BACnet Stack Improperly Limits Pathnames to a Restricted Directory","id":"CVE-2026-21878","kev_date_added":null,"published":"2026-02-13"},{"cvss_score":7.5,"headline":"BACnet-stack MS/TP reply matcher OOB read","id":"CVE-2025-66624","kev_date_added":null,"published":"2025-12-05"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"poc","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-04-21","vendors":["bacnet-stack"]},"summary":"Undefined behavior from signed left shifts in BACnet Stack can cause crashes or unpredictable behavior when processing specific BACnet data.","url":"https://insights.sbomify.com/CVE-2026-40279/"}