CVE-2026-31393

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

Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access

l2cap_information_rsp() checks that cmd_len covers the fixed l2cap_info_rsp header (type + result, 4 bytes) but then reads rsp->data without verifying that the payload is present:

• L2CAP_IT_FEAT_MASK calls get_unaligned_le32(rsp->data), which reads 4 bytes past the header (needs cmd_len >= 8).

• L2CAP_IT_FIXED_CHAN reads rsp->data[0], 1 byte past the header (needs cmd_len >= 5).

A truncated L2CAP_INFO_RSP with result == L2CAP_IR_SUCCESS triggers an out-of-bounds read of adjacent skb data.

Guard each data access with the required payload length check. If the payload is too short, skip the read and let the state machine complete with safe defaults (feat_mask and remote_fixed_chan remain zero from kzalloc), so the info timer cleanup and l2cap_conn_start() still run and the connection is not stalled.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/187e6fe939295be36063a1d91f8bebee04399a8c
• https://git.kernel.org/stable/c/3b646516cba2ebc4b51a72954903326e7c1e443f
• https://git.kernel.org/stable/c/5229e7d15771eac2b5886bfb1f976aea0c1eec14
• https://git.kernel.org/stable/c/807bd1258453c4c83f6ae9dbc1e7b44860ff40d0
• https://git.kernel.org/stable/c/9aeacde4da0f02d42fd968fd32f245828b230171
• https://git.kernel.org/stable/c/db2872d054e467810078e2b9f440a5b326a601b2
• https://git.kernel.org/stable/c/dd815e6e3918dc75a49aaabac36e4f024d675101
• https://git.kernel.org/stable/c/e7ff754e339e3d5ce29aa9f95352d0186df8fbd9