CVE
BACnet Stack denial of service in AtomicWriteFile record decoder
Affects bacnet-stack deployments that enable AtomicWriteFile and use its record-access variant. Fixed in 1.4.4 and 1.5.1.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- Proof of concept public, per CISA
- Fix
- Fixed in 1.4.4, 1.5.1
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.4.4, 1.5.1.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.43% · 37th percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 43/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: poc
- Automatable: yes
- Technical impact: partial
Summary
The BACnet Stack library has an out-of-bounds read flaw in how its AtomicWriteFile record decoder handles a record count supplied by the sender. A remote attacker on the network can trigger it without logging in, and the impact described is a denial of service (availability), not data disclosure.
Read the original description
BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to versions 1.4.4 and 1.5.1, an out-of-bounds read vulnerability exists in bacnet-stack's AtomicWriteFile record-access path. The bug is caused by a mismatch between an externally controlled returnedRecordCount field and the fixed-size internal fileData[] array used by BACNET_ATOMIC_WRITE_FILE_DATA. This issue has been patched in versions 1.4.4 and 1.5.1.
Who should check
Teams building or shipping bacnet-stack C library builds up to 1.5.0 with AtomicWriteFile enabled, including embedded BACnet/IP devices.
Read the source excerpt
“The vulnerable path is reachable before authentication in the normal BACnet service dispatch flow if AtomicWriteFile is enabled in the target deployment.”
cve.now Index
- Exploitation15/40CISA rates a proof of concept as public
- Exposure20/25No login or user action needed, CISA rates it automatable · Unknown: Advisories don't say whether default setups are affected
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 73 if added to CISA KEV
- Would score about 68 if CISA's SSVC rates exploitation active
- Would score about 48 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 1.4.4, 1.5.1.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-46674 (BACnet Stack: Out-of-Bounds Read in AtomicWriteFile Record Decoder via Unbounded returnedRecordCount), 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-2026-46674 (entry last updated 2026-11-13):
Affected:
- bacnet-stack bacnet-stack: fixed in 1.4.4; fixed in 1.5.1
Fixed versions: 1.4.4, 1.5.1.
Conditions (all must be true for the bug to be hit):
- AtomicWriteFile record-access variant is used (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-8384-pwhh-cxjh)
- AtomicWriteFile is enabled in the deployment (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-8384-pwhh-cxjh)
- BACNET_WRITE_FILE_RECORD_COUNT defaults to 1, so fileData holds one element (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-8384-pwhh-cxjh)
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-2026-46674 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-46674 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-8384-pwhh-cxjh
- https://github.com/bacnet-stack/bacnet-stack/pull/1344
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-2026-46674
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-2026-46674"}.Timeline
- CVE published
- First seen by cve.now1 day
- CISA SSVC assessment
Exploitation: poc · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- bacnet-stack bacnet-stack
fixed in 1.4.4; fixed in 1.5.1
Evidence 4
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 1
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-46674
Is CVE-2026-46674 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: cve.now feed data
What does this mean?
A crafted AtomicWriteFile request can make the implementation read beyond a stack-allocated object. This can crash the process or cause denial of service, mainly in sanitizer or instrumented builds.Source: github.com
Which versions are affected by CVE-2026-46674?
bacnet-stack: before 1.4.4; before 1.5.1.Source: cve.now feed data
Am I affected, and how do I check?
The issue is tied to the record-access variant of AtomicWriteFile, and only when AtomicWriteFile is enabled in the deployment. The default BACNET_WRITE_FILE_RECORD_COUNT of 1 is defined in src/bacnet/awf.h. To check, confirm the bacnet-stack version in use and whether AtomicWriteFile is enabled in the build configuration.Source: github.com
How do I fix CVE-2026-46674?
Upgrade to bacnet-stack 1.4.4 or 1.5.1, depending on which release line is in use.Source: github.com