High [CVE-2026-68121] Linux kernel: PPPoE memory corruption via stale pointer
This high-severity Red Hat Linux advisory covers CVE-2026-68121 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
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.
A flaw was found in the Linux kernel's PPPoE (Point-to-Point Protocol over Ethernet) implementation. This vulnerability occurs because a pointer to network packet data is not updated after memory is reallocated, leading to the use of an outdated memory address.
An attacker with local access could potentially trigger this condition, causing memory corruption. This could result in a system crash (denial of service) or other unpredictable system behavior.
Red Hat severity: Moderate — CVSS 7.3 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H). Weakness: CWE-825.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 30 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 30 days ago·verify at source
Mitigation checklist
- If PPPoE functionality is not required, prevent the `pppoe` kernel module from loading to mitigate this vulnerability. This can be achieved by creating a modprobe configuration file. A system reboot is required for the changes to take effect. ```bash echo "install pppoe /bin/true" > /etc/modprobe.d/disable-pppoe.conf ```
Official advisory · high-confidence parse· fetched 30 days ago·verify at source
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