CVE-2025-38108 net_sched: red: fix a race in __red_change()
A race condition in the Linux kernel's RED qdisc allows an attacker to underflow queue length, potentially causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-38108?
CVE-2025-38108 is a high-severity vulnerability in Debian Debian Linux, published on 3 Jul 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net_sched: red: fix a race in __red_change()
Gerrard Tai reported a race condition in RED, whenever SFQ perturb timer fires at the wrong time.
The race is as follows:
CPU 0 CPU 1 [1]: lock root [2]: qdisc_tree_flush_backlog() [3]: unlock root | | [5]: lock root | [6]: rehash | [7]: qdisc_tree_reduce_backlog() | [4]: qdisc_put()
This can be abused to underflow a parent's qlen.
Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog() should fix the race, because all packets will be purged from the qdisc before releasing the lock.
Weakness: CWE-362
Which versions are affected by CVE-2025-38108?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-38108?
Apply the vendor's patch.
Is CVE-2025-38108 being exploited?
There is no known exploitation of CVE-2025-38108 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-64622, BELL-CVE-2025-38108, DEBIAN-CVE-2025-38108, GHSA-3vxj-mcrg-4r6j, ROOT-OS-DEBIAN-11-CVE-2025-38108, ROOT-OS-DEBIAN-12-CVE-2025-38108 and 3 more.