# CVE-2026-41503: BACnet Stack: Out-of-Bounds Read in ReadPropertyMultiple Property Decoder via Deprecated Tag Parser

> Unauthenticated remote attackers can cause crashes or read memory via out-of-bounds read in BACnet Stack's ReadPropertyMultiple decoder.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Apr 2026
- **Updated:** 27 Apr 2026
- **Also known as:** GHSA-5w2v-mwqj-pr2c

## What is CVE-2026-41503?

CVE-2026-41503 is a high-severity memory corruption vulnerability in bacnet-stack, published on 24 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an out-of-bounds read vulnerability in bacnet-stack's ReadPropertyMultiple service property decoder allows unauthenticated remote attackers to read past allocated buffer boundaries by sending an RPM request with a truncated property list. The vulnerability stems from rpm_decode_object_property() calling the deprecated decode_tag_number_and_value() function at src/bacnet/rpm.c:344, which accepts no buffer length parameter and reads blindly from whatever pointer it receives. A crafted BACnet/IP packet with a 1-byte property payload containing an extended tag marker (0xF9) causes the decoder to read 1 byte past the end of the buffer, leading to crashes on embedded BACnet devices. The vulnerability exists in src/bacnet/rpm.c and affects any deployment that enables the ReadPropertyMultiple confirmed service handler (enabled by default in the reference server). This vulnerability is fixed in 1.4.3.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-41503?

It affects 1 product.


Products: Bacnetstack Bacnet Stack.

## How do I fix CVE-2026-41503?

No fix has been published for CVE-2026-41503 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-41503 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-41503 exists.

## Other vulnerabilities in bacnet-stack

- [CVE-2023-51773](https://insights.sbomify.com/CVE-2023-51773/): Memory corruption in n/a (critical 9.1)
- [CVE-2026-41475](https://insights.sbomify.com/CVE-2026-41475/): BACnet Stack: Out-of-Bounds Read in WritePropertyMultiple Decoder via Deprecated Tag Parser (high 8.7)
- [CVE-2026-41502](https://insights.sbomify.com/CVE-2026-41502/): BACnet Stack: Off-by-One Out-of-Bounds Read in ReadPropertyMultiple Object ID Decoder (high 8.7)
- [CVE-2026-26264](https://insights.sbomify.com/CVE-2026-26264/): BACnet Stack WriteProperty decoding length underflow leads to OOB read and crash (high 7.8)
- [CVE-2026-21878](https://insights.sbomify.com/CVE-2026-21878/): BACnet Stack Improperly Limits Pathnames to a Restricted Directory (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-41503 and fix it if it is affected.

What it is: CVE-2026-41503 is a high-severity memory corruption vulnerability in bacnet-stack, published on 24 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-41503 exists.

Affected product: bacnet-stack. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-41503/ (Markdown: https://insights.sbomify.com/CVE-2026-41503/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-41503
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41503
- OSV: https://osv.dev/vulnerability/CVE-2026-41503

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-41503/
Summaries are generated and may contain mistakes; the official description above is the record.