Medium [CVE-2026-64403] validate option length before reading conf opt value
This medium-severity Red Hat Linux advisory covers CVE-2026-64403 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8.
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Summary
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.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 12 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 12 hours ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Official advisory · high-confidence parse· fetched 12 hours ago·verify at source
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