CVE-2026-68121 pppoe: reload header pointer after dev_hard_header()
A use-after-free vulnerability in the Linux kernel PPPoE module allows attackers to execute arbitrary code or escalate privileges via crafted network packets.
- 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-2026-68121?
CVE-2026-68121 is a high-severity use after free vulnerability in Linux, published on 10 Aug 2026. 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:
pppoe: reload header pointer after dev_hard_header()
pppoe_sendmsg() saves a pointer to the PPPoE header before calling dev_hard_header(). Device header callbacks are allowed to reallocate the skb head, invalidating pointers into it.
This can happen when a send is blocked in copy_from_user() while the first non-Ethernet port is added to an empty team device. The team's delegated GRE header callback then expands the skb head. PPPoE subsequently writes six bytes through the stale pointer into the freed head.
Reload the PPPoE header through the skb's network-header offset after device header creation. pskb_expand_head() updates that offset when it relocates the head.
Weakness: CWE-416
Which versions are affected by CVE-2026-68121?
How do I fix CVE-2026-68121?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-68121 being exploited?
There is no known exploitation of CVE-2026-68121 in the wild and no public exploit code.
Public exploit code: 3 proofs of concept on GitHub.
Sources
Also known as BELL-CVE-2026-68121, DEBIAN-CVE-2026-68121, GHSA-7hvc-v975-w6v4, UBUNTU-CVE-2026-68121.