CVE-2026-68121 — Linux Vulnerability Details

What is CVE-2026-68121?

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.

Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 74 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 7.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST): 0.2% probability of exploitation in the next 30 days, higher than 20.6% of all scored CVEs
CISA KEV: Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority: 6.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published: 2026-08-10, last modified 2026-08-19

Is CVE-2026-68121 being exploited?

Weaponised exploit code for CVE-2026-68121 is publicly available. 3 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 33 in the Threadlinqs vulnerability feed.

Affected products and versions

Linux: Linux

How to fix CVE-2026-68121

No vendor patch reference has been recorded for CVE-2026-68121 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-68121

1 tracked threat in the Threadlinqs corpus references CVE-2026-68121, either in the campaign’s CVE list or as an indicator on the campaign record.

"LPE Quartet": Public Exploits Released for Four Linux Kernel Local-Root Flaws (DirtyAH6, TUNderflow, PPPoEject, DiagSpill) — HIGH · 2026-09-18

Sources

Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-10-10.

Other references

Showing 5 of 8 recorded references.