CVE-2026-80975
CVE-2026-80975 is a security vulnerability. O3 Security confirms whether CVE-2026-80975 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
In the Linux kernel, the following vulnerability has been resolved: mfd: qnap-mcu: keep the reply buffer alive past a command timeout qnap_mcu_exec() publishes an on-stack buffer…
Description
In the Linux kernel, the following vulnerability has been resolved:
mfd: qnap-mcu: keep the reply buffer alive past a command timeout
qnap_mcu_exec() publishes an on-stack buffer to the receive path:
unsigned char rx[QNAP_MCU_RX_BUFFER_SIZE];
...
reply->data = rx;
reply->length = length;
and qnap_mcu_receive_buf() writes into it from the serdev receive path, which runs out of flush_to_ldisc() and is not serialized against qnap_mcu_exec() at all. bus_lock cannot cover it, because qnap_mcu_exec() holds that mutex across wait_for_completion_timeout().
On a timeout qnap_mcu_exec() returns with reply->data still pointing at its own frame. A reply that arrives late, or an unsolicited message from the MCU, is then written into a stack frame that has been left, corrupting whatever runs next on that stack. The same applies when qnap_mcu_write() fails, since that path returns without touching the reply state either.
Move the receive buffer into struct qnap_mcu. It is 37 bytes and the structure is devm_kzalloc()ed, so it lives as long as the driver, and a late write lands in memory that is still valid and is reinitialized by the next command. bus_lock keeps commands from sharing it.
This deliberately does not clear reply->data or reply->length on the timeout path. Doing so races with qnap_mcu_receive_buf(), which reads both after its
if (!reply->length)
return size;
check: clearing reply->data gives a NULL dereference, and clearing reply->length alone removes the reply->received == reply->length exit condition, so the copy loop runs until the uart chunk is consumed and overruns the buffer. Leaving both set keeps the write bounded by reply->length, which qnap_mcu_exec() has already checked against sizeof(mcu->rx).
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-80975 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-80975 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-80975. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-80975 in your dependencies?
O3 detects CVE-2026-80975 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.