CVE-2024-26826 mptcp: fix data re-injection from stale subflow
A logic error in the Linux kernel MPTCP scheduler prevents data re-injection from stale subflows, potentially causing connection stalls or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-26826?
CVE-2024-26826 is a high-severity denial of service vulnerability in Linux kernel, published on 17 Apr 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mptcp: fix data re-injection from stale subflow
When the MPTCP PM detects that a subflow is stale, all the packet scheduler must re-inject all the mptcp-level unacked data. To avoid acquiring unneeded locks, it first try to check if any unacked data is present at all in the RTX queue, but such check is currently broken, as it uses TCP-specific helper on an MPTCP socket.
Funnily enough fuzzers and static checkers are happy, as the accessed memory still belongs to the mptcp_sock struct, and even from a functional perspective the recovery completed successfully, as the short-cut test always failed.
A recent unrelated TCP change - commit d5fed5addb2b ("tcp: reorganize tcp_sock fast path variables") - exposed the issue, as the tcp field reorganization makes the mptcp code always skip the re-inection.
Fix the issue dropping the bogus call: we are on a slow path, the early optimization proved once again to be evil.
Which versions are affected by CVE-2024-26826?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-26826?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-26826 being exploited?
There is no known exploitation of CVE-2024-26826 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-26826, DEBIAN-CVE-2024-26826, GHSA-vfr6-9rmm-7rvg, UBUNTU-CVE-2024-26826.