CVE-2026-64403
HighCVSS 7.1Exploitation Probability (EPSS)
Low risk18th percentile - higher than 18% of all known CVEs
Summary
In the Linux kernel Bluetooth L2CAP stack, l2cap_get_conf_opt() reads the option value before verifying that the full option fits in the buffer, allowing an attacker-controlled length to cause an out-of-bounds read of up to 4 bytes.
Risk Assessment
This vulnerability could lead to kernel memory disclosure or potential system instability, although the out-of-bounds value is currently not consumed. It is a validate-after-use ordering bug.
Recommendation
Apply the Linux kernel patch that modifies l2cap_get_conf_opt() to validate the option length before reading the value, and update your system to a version containing this fix.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: validate option length before reading conf opt value l2cap_get_conf_opt() derives the option length from the attacker-controlled opt->len field and immediately dereferences opt->val (as u8, get_unaligned_le16() or get_unaligned_le32(), or a raw pointer for the default case) before any caller has confirmed that opt->len bytes are present in the buffer. The callers (l2cap_parse_conf_req(), l2cap_parse_conf_rsp() and l2cap_conf_rfc_get()) only detect a malformed option afterwards, once the running length has gone negative, by which point the out-of-bounds read has already executed. An existing post-hoc length check keeps the garbage value from being consumed, so this is not a data leak in the current control flow. It is still a validate-after-use ordering bug: up to 4 bytes are read past the end of the buffer before it is known to contain them, and it is fragile to future changes in the callers. Fix it at the source. Pass the end of the buffer into l2cap_get_conf_opt() and refuse to touch opt->val unless the full option (header + value) fits. Each caller computes an end pointer once before the loop and checks the return value directly instead of inferring the error from a negative length.