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CVE-2025-66624

HIGHCVSS 7.5/10EPSS 0.35%

Last modified

CVE-2025-66624 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. Prior to 1.5.0.rc2, The npdu_is_expected_reply function in src/bacnet/npdu.c indexes request_pdu[offset+2/3/5] and reply_pdu[offset+1/2/4] without verifying that those APDU bytes exist. EPSS estimates a 0.35% chance of exploitation in the next 30 days.

Description

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. Prior to 1.5.0.rc2, The npdu_is_expected_reply function in src/bacnet/npdu.c indexes request_pdu[offset+2/3/5] and reply_pdu[offset+1/2/4] without verifying that those APDU bytes exist. bacnet_npdu_decode() can return offset == 2 for a 2-byte NPDU, so tiny PDUs pass the version check and then get read out of bounds. On ASan/MPU/strict builds this is an immediate crash (DoS). On unprotected builds it is undefined behavior and can mis-route replies; RCE is unlikely because only reads occur, but DoS is reliable.

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability
0.35%

27.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersionsUpdate
BacnetstackBacnet Stack1.5.0Rc1

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2025-66624?
BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. Prior to 1.5.0.rc2, The npdu_is_expected_reply function in src/bacnet/npdu.c indexes request_pdu[offset+2/3/5] and reply_pdu[offset+1/2/4] without verifying that those APDU bytes exist. bacnet_npdu_decode() can return offset == 2 for a 2-byte NPDU, so tiny PDUs pass the version check and then get read out of bounds. On ASan/MPU/strict builds this is an immediate crash (DoS). On unprotected builds it is undefined behavior and can mis-route replies; RCE is unlikely because only reads occur, but DoS is reliable.
How severe is CVE-2025-66624?
CVE-2025-66624 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.35% probability of exploitation in the next 30 days.
How do I fix CVE-2025-66624?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-66624?

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Source: NVD / NIST