CVE-2026-45812 is a CWE-131 vulnerability in Apache NimBLE through version 1.9.0, involving incorrect calculation of buffer size when handling Legacy Advertising Report HCI events that contain multiple bundled reports. NimBLE miscalculates the offset to the next report, potentially causing the host to read past the buffer boundary and deliver corrupted GAP event data to the application. The vulnerability is of medium severity (CVSS 6.5) and primarily relevant when NimBLE's host is paired with third-party controllers that batch multiple reports, as NimBLE's own controller does not exhibit this behavior. The issue is fixed in Apache NimBLE version 1.10.0.

The vulnerability can lead to the host reading beyond the intended buffer, resulting in delivery of bogus GAP event data to the application. This may cause data integrity issues but does not impact confidentiality, integrity, or availability beyond corrupted event data. The risk is limited because NimBLE's own controller does not batch multiple reports, so exploitation requires pairing with a third-party controller that does.

Users should upgrade Apache NimBLE to version 1.10.0 or later, where this buffer size miscalculation issue is fixed. No other mitigation is indicated or required.