CVE-2026-62977
BACnet Stack: `WriteProperty(File_Size)` can bypass read-only protection and expose uninitialized RAMFS tail bytes through `AtomicReadFile`
Description
BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to version 1.5.1, the BACnet FILE object implementation allows remote WriteProperty(PROP_FILE_SIZE) requests to change the size of a stream-access FILE object without checking whether that FILE is marked Read_Only. When the FILE backend is RAMFS, enlarging the file only performs realloc() and updates the stored size; the newly exposed tail region is not initialized before later reads. As a result, a remote client can enlarge a read-only RAMFS-backed stream-access FILE and then immediately retrieve the newly exposed region with AtomicReadFile(stream-access). Depending on the allocator and build configuration, the returned data may contain sanitizer fill bytes, stale heap contents, or other unintended process memory. Shrinking the file through the same path can also remotely truncate content that was intended to be read-only. This issue has been patched in versions 1.5.1 and 1.6.0.
INFO
Published Date :
Nov. 13, 2026, 7:19 p.m.
Last Modified :
Nov. 13, 2026, 7:19 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update BACnet Stack to version 1.5.1 or later.
- Apply vendor-supplied patches for the BACnet stack.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-62977.
| URL | Resource |
|---|---|
| https://github.com/bacnet-stack/bacnet-stack/pull/1411 | |
| https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-mwj7-2v5r-v934 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-62977 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-62977
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-62977 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-62977 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Nov. 13, 2026
Action Type Old Value New Value Added Description BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to version 1.5.1, the BACnet FILE object implementation allows remote WriteProperty(PROP_FILE_SIZE) requests to change the size of a stream-access FILE object without checking whether that FILE is marked Read_Only. When the FILE backend is RAMFS, enlarging the file only performs realloc() and updates the stored size; the newly exposed tail region is not initialized before later reads. As a result, a remote client can enlarge a read-only RAMFS-backed stream-access FILE and then immediately retrieve the newly exposed region with AtomicReadFile(stream-access). Depending on the allocator and build configuration, the returned data may contain sanitizer fill bytes, stale heap contents, or other unintended process memory. Shrinking the file through the same path can also remotely truncate content that was intended to be read-only. This issue has been patched in versions 1.5.1 and 1.6.0. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-284 Added CWE CWE-908 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/62xxx/CVE-2026-62977.json">CVE-2026-62977</a> Added Reference https://github.com/bacnet-stack/bacnet-stack/pull/1411 Added Reference https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-mwj7-2v5r-v934