CVE-2024-36016

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

tty: n_gsm: fix possible out-of-bounds in gsm0_receive()

Assuming the following:

- side A configures the n_gsm in basic option mode

- side B sends the header of a basic option mode frame with data length 1

- side A switches to advanced option mode

- side B sends 2 data bytes which exceeds gsm->len

Reason: gsm->len is not used in advanced option mode.

- side A switches to basic option mode

- side B keeps sending until gsm0_receive() writes past gsm->buf

Reason: Neither gsm->state nor gsm->len have been reset after

reconfiguration.

Fix this by changing gsm->count to gsm->len comparison from equal to less

than. Also add upper limit checks against the constant MAX_MRU in

gsm0_receive() and gsm1_receive() to harden against memory corruption of

gsm->len and gsm->mru.

All other checks remain as we still need to limit the data according to the

user configuration and actual payload size.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References