CVE
BACnet Stack out-of-bounds read in AtomicReadFile-ACK handling
- Exploited
- No known exploitation
- 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? →
- 0.22% · 12th 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? →
- 14/100 · provisional
- 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
Summary
BACnet Stack, a BACnet protocol library for embedded systems, has an out-of-bounds read in its client-side handling of AtomicReadFile acknowledgement records. A remote device can trigger it over the network without logging in, but it requires a user to take an action, and the flaw can crash the affected client.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
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, there is a client-side out-of-bounds read in the AtomicReadFile-ACK record-access handling path. The issue is caused by a mismatch between a remote returnedRecordCount value and the fixed local fileData[] array capacity in BACNET_ATOMIC_READ_FILE_DATA. The ACK decode path preserves the remote RecordCount, discards storage for excess records without truncating that count, and a downstream sink later iterates over the original RecordCount and indexes fileData[i] out of bounds. This issue has been patched in versions 1.4.4 and 1.5.1.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure7/25Reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity6.5/10CVSS 6.5
- No patch0/5No signal
What would change the score
- Would score about 69 if added to CISA KEV
- Would score about 64 if CISA's SSVC rates exploitation active
- Would score about 29 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-2026-46677 (BACnet Stack: Client-Side Out-of-Bounds Read in AtomicReadFile-ACK Record-Access Handling via RecordCount / fileData[] Mismatch), 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-2026-46677 (entry last updated 2026-11-12):
Affected:
- bacnet-stack bacnet-stack: fixed in 1.4.4; fixed in 1.5.1
Fixed versions: 1.4.4, 1.5.1.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-46677 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-46677 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-rv5h-cxwq-q3mh
- 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-2026-46677
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-2026-46677"}.Timeline
- CVE published
- First seen by cve.now
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-2026-46677
Is CVE-2026-46677 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: cve.now feed data
Which versions are affected by CVE-2026-46677?
bacnet-stack: before 1.4.4; before 1.5.1.Source: cve.now feed data
How do I fix CVE-2026-46677?
Upgrade to a fixed version: 1.4.4, 1.5.1.Source: cve.now feed data