CVE-2026-64027: net: shaper: rework the VALID marking (again)
In the Linux kernel, the following vulnerability has been resolved:
net: shaper: rework the VALID marking (again)
Recent commit changed the semantics from NOTVALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant.
The biggest consequence of this is that we may see a UAF since netshaperrollback() assumed that entries without VALID can be freed without observing RCU.
Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smploadacquire() / smpstorerelease() barriers are marginally cleaner.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-64027?
CVE-2026-64027 has a risk rating of 47, indicating a moderate severity level.
How do I fix CVE-2026-64027?
To fix CVE-2026-64027, update to the latest patched version of the Linux kernel where this vulnerability has been addressed.
What are the potential impacts of CVE-2026-64027?
CVE-2026-64027 may allow for race conditions that could lead to unintended information exposure or system instability.
Which systems are affected by CVE-2026-64027?
CVE-2026-64027 affects various versions of the Linux kernel that implement the net shaper component.
Is CVE-2026-64027 actively being exploited?
As of the latest information, there are no known active exploits for CVE-2026-64027.