---
id: "CVE-2026-62975"
page: "https://infrastack.ai/live/CVE-2026-62975"
kind: "vulnerability"
aliases: ["CVE-2026-62975"]
title: "BACnet Stack: RAMFS record replace reads past heap buffer"
severity: "medium"
cvss: 6.9
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "BACnet Stack", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["bacnet", "c", "embedded", "iot", "package"]
not_affected_if: ["file-services-disabled", "no-ramfs-file-backend"]
published_at: "2026-11-13T19:19:32+00:00"
first_seen_at: "2026-11-13T19:52:09+00:00"
updated_at: "2026-11-13T19:54:12+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62975", "first_seen_at": "2026-11-13T19:52:09+00:00"}]
exploit_sources: []
---

# BACnet Stack: RAMFS record replace reads past heap buffer

Link for people: https://infrastack.ai/live/CVE-2026-62975 (this .md is for agents)

BACnet Stack's RAMFS-backed file code, used in AtomicWriteFile record-access requests, can shrink a heap buffer and then copy using a stale length. An attacker can cause an out-of-bounds heap read, which can leak memory contents or crash the process.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:BACnet Stack affected range not listed fixed no fixed version listed

## How to check

- Check the BACnet Stack version in your build or lockfile; affected versions are those before `1.5.1`.
- Look for the RAMFS FILE backend (AtomicWriteFile record-access handling) in the build configuration.

## Fix

- Move to `1.5.1` or `1.6.0`, the patched versions named in the advisory.

## Timeline

- 2026-11-13T19:52:09+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-62975

## Documents

- [advisory] Vendor advisory: github.com https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-cf8g-hp9m-9fvv

## From the sources

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to version 1.5.1, the RAMFS-backed FILE implementation accepts AtomicWriteFile(record-access) requests that replace existing records with caller-controlled content. If a client replaces a record with shorter data, the backend can shrink the heap allocation and then continue processing with a trailing-copy length derived from the old layout. During that replace path, the RAMFS backend computes the trailing-copy length from the old file layout, then shrinks the heap allocation, and finally uses the stale length in memmove(). As a result, the source range of that memmove() can extend beyond the end of the reallocated heap buffer, producing a heap out-of-bounds read. This issue has been patched in versions 1.5.1 and 1.6.0.

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