CVE
BACnet Stack man-in-the-middle via hub certificate validation flaw
Affects bacnet-stack BACnet/SC nodes using the websocket client in ports/linux, ports/bsd or ports/win32. Fixed in 1.4.6, 1.5.2 and 1.6.1.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- Exploited
- No known exploitation
- Fix
- Fixed in 1.4.6, 1.5.2, 1.6.1
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.4.6, 1.5.2, 1.6.1.
- 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? →
- 0.20% · 10th 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? →
- 8/100 · 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
Summary
A flaw in the bacnet-stack library causes its BACnet/SC node to accept a self-signed certificate from any hub, even one that does not chain to the trusted CA. An attacker on an adjacent network, without logging in or any user action, can impersonate the hub, obtain the node's identity, and read all later BACnet traffic.
Original 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, bws_cli_connect() in ports/linux/websocket-cli.c loads the trusted CA cert into the libwebsockets context, then always sets LCCSCF_ALLOW_SELFSIGNED in the connection flags. So lws accepts any self-signed hub certificate, whether or not it chains to the loaded CA. A BACnet/SC node finishes the TLS handshake to a rogue hub that presents a self-signed cert. It then hands the attacker its identity (VMAC, UUID) and all later BACnet traffic. This issue has been patched in versions 1.4.6, 1.5.2, 1.6.1, and 1.7.0.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. Advisories don't say whether default setups are affected
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.7/10CVSS 7.7
- No patch0/5No signal
What would change the score
- Would score about 63 if added to CISA KEV
- Would score about 58 if CISA's SSVC rates exploitation active
- Would score about 30 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 1.4.6, 1.5.2, 1.6.1.
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-2026-102537 (bacnet-stack BACnet/SC node always accepts a self-signed hub cert, so an attacker can MITM it), 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-2026-102537 (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):
- Uses the BACnet/SC websocket client in ports/linux, ports/bsd or ports/win32 (the reference BACnet/SC datalink port) (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-jgm4-2wg9-jwfg)
- Attacker must be able to intercept or impersonate the hub endpoint (on-path, DNS/ARP spoofing, or network redirect) (source: https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-jgm4-2wg9-jwfg)
Setup: the bug is reachable in a default setup; no special feature or setting is needed.
Attacker needs: adjacent access, no login, no user action.
CISA KEV: CVE-2026-102537 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-102537 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-jgm4-2wg9-jwfg
- https://github.com/bacnet-stack/bacnet-stack/pull/1434
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-2026-102537
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-2026-102537"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- 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
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-2026-102537
Is CVE-2026-102537 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
What does this mean?
The BACnet/SC node accepts a self-signed certificate from a rogue hub. An attacker who intercepts or impersonates the hub can then obtain the node's identity (VMAC and UUID) and all later BACnet traffic.Source: github.com
Which versions are affected by CVE-2026-102537?
bacnet-stack: before 1.4.6; from 1.5.0 before 1.5.2; from 1.6.0 before 1.6.1.Source: cve.now feed data
Am I affected, and how do I check?
Versions before 1.4.6, versions from 1.5.0 before 1.5.2, and versions from 1.6.0 before 1.6.1. The issue applies to builds that use the BACnet/SC websocket client in ports/linux, ports/bsd or ports/win32. Check the bacnet-stack version in use and whether the build uses that websocket client.Source: github.com
How do I fix CVE-2026-102537?
Upgrade to 1.4.6, 1.5.2 or 1.6.1, matching the release line in use.Source: github.com