CVE-2024-48981: mbed Buffer Overflow — Fix

Description

An issue was discovered in MBed OS 6.16.0. During processing of HCI packets, the software dynamically determines the length of the packet header by looking up the identifying first byte and matching it against a table of possible lengths. The initial parsing function, hciTrSerialRxIncoming does not drop packets with invalid identifiers but also does not set a safe default for the length of unknown packets' headers, leading to a buffer overflow. This can be leveraged into an arbitrary write by an attacker. It is possible to overwrite the pointer to a not-yet-allocated buffer that is supposed to receive the contents of the packet body. One can then overwrite the state variable used by the function to determine which state of packet parsing is currently occurring. Because the buffer is allocated when the last byte of the header has been copied, the combination of having a bad header length variable that will never match the counter variable and being able to overwrite the state variable with the resulting buffer overflow can be used to advance the function to the next step while skipping the buffer allocation and resulting pointer write. The next 16 bytes from the packet body are then written wherever the corrupted data pointer is pointing.

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CVSS v3.1 Score

7.5

HIGH

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

Weakness Type (CWE)

CWE-120 CWE-120

Affected Products

Vendor	Product	Versions
arm	mbed	All

References

Advisories & Patches

https://github.com/mbed-ce/mbed-os/pull/374

Other References

https://github.com/mbed-ce/mbed-os/blob/54e8693ef4ff7e025018094f290a1d5cf380941f/connectivity/FEATURE_BLE/source/cordio/stack_adaptation/hci_tr.c#L161

Frequently Asked Questions

What is CVE-2024-48981? +

An issue was discovered in MBed OS 6.16.0. During processing of HCI packets, the software dynamically determines the length of the packet header by looking up the identifying first byte and matching it against a table of possible lengths. The initial parsing function, hciTrSerialRxIncoming does not drop packets with invalid identifiers but also does not set a safe default for the length of unknown packets' headers, leading to a buffer overflow. This can be leveraged into an arbitrary write by an attacker. It is possible to overwrite the pointer to a not-yet-allocated buffer that is supposed to receive the contents of the packet body. One can then overwrite the state variable used by the function to determine which state of packet parsing is currently occurring. Because the buffer is allocated when the last byte of the header has been copied, the combination of having a bad header length variable that will never match the counter variable and being able to overwrite the state variable with the resulting buffer overflow can be used to advance the function to the next step while skipping the buffer allocation and resulting pointer write. The next 16 bytes from the packet body are then written wherever the corrupted data pointer is pointing. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2024-48981? +

CVE-2024-48981 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2024-48981? +

CVE-2024-48981 affects products from arm, specifically: mbed. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-48981? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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