CVE-2026-68121

pppoe: reload header pointer after dev_hard_header()

No known exploitation. EPSS puts it in the 6th percentile. No fix published yet.

CVSS 3.17.8High EPSS percentile6th0.2% chance in 30 days CISA KEVNot listedNo confirmed exploitation
No public exploit known FixNone yetNo fix or workaround published

Published 2026-08-10Updated 2026-08-19Sources: CVE.org, NVD

NVD CVE.org

What to do

No fixed build or workaround is published yet. Limit exposure and watch for a patch.

Steps

Written by AI from the record

Ask your IT provider whether any Linux systems or network appliances use PPPoE, team networking, and GRE.
Update to your vendor's kernel release containing the applicable fix commit: 7a56e7c9b08e08fd55a1bcada24cf4fe3782b722, 6eed5ae7887a93160803d2b81ff88e75eefd4a4c, ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a, e6493a4d1ee17595766165fa446d45b7e0c318d0, 7e9fbd7f96bcde63a7c798fe16b38cedee7a1501, 6866abf59976d273164a6624234d96a967280223, bed4caecd723693f750e13adbb2c42ca1249a3fd, or e9c238f6fe42fb1b4dba3a578277de32cb487937.
If an update cannot be installed promptly, disable unused PPPoE or the affected team/GRE network setup and limit untrusted local accounts.
Restart updated systems during a planned maintenance window so they begin using the new kernel.

Usually a quick update

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

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.

In plain language

Written by AI from the record

This is a serious Linux kernel flaw affecting systems with PPPoE configured; small businesses should have their IT provider update affected servers and network appliances promptly.

A local, low-privilege attacker can trigger a use-after-free write in Linux kernel PPPoE packet transmission when dev_hard_header() reallocates the skb head, potentially leading to kernel code execution.

If you're affected

Full server takeover
Network appliance compromise
Business service outage
Sensitive data exposure
Ransomware risk

What is it

A flaw in the Linux kernel can let a logged-in attacker make the system write information into the wrong area of its own memory. It is like a delivery worker being handed an old warehouse shelf number after the stock has been moved: the package can be placed somewhere it should never go, potentially bringing down or taking control of the system.

Who is affected

This matters if you run Linux kernel systems or network appliances that use PPPoE networking. This includes environments where a local user can run programs on the affected machine. It is only a risk when PPPoE is configured and the specific team-device/GRE network path can be triggered.

How urgent is it

Attackers are already exploiting this vulnerability, so treat it as an urgent remediation item. Prioritize exposed business servers, shared systems, and network appliances where untrusted users can obtain local access; no public exploit code is currently recorded.

What to do — in detail

Confirm whether PPPoE is enabled and whether the host uses a team device with GRE headers; the vulnerable path requires a PPPoE send operation while the device header callback reallocates the socket buffer. Obtain a kernel package from the operating-system, appliance, or cloud vendor that includes the relevant backport; the findings identify fixes by commit rather than release-version number: 7a56e7c9b08e08fd55a1bcada24cf4fe3782b722, 6eed5ae7887a93160803d2b81ff88e75eefd4a4c, ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a, e6493a4d1ee17595766165fa446d45b7e0c318d0, 7e9fbd7f96bcde63a7c798fe16b38cedee7a1501, 6866abf59976d273164a6624234d96a967280223, bed4caecd723693f750e13adbb2c42ca1249a3fd, or e9c238f6fe42fb1b4dba3a578277de32cb487937. This is a targeted kernel bug fix; no breaking-change information was provided. If patching is delayed, disable unused PPPoE and avoid the team/GRE configuration that makes the condition reachable, while restricting untrusted local accounts. No CISA remediation due date was provided. Monitor for unexpected kernel crashes, unusual local process activity, and changes to PPPoE, team, or GRE networking configuration.

Technical context

Severity is CVSS 7.8 High (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). The issue is a stale PPPoE header pointer/use-after-free-style invalid-memory write in pppoe_sendmsg(): dev_hard_header() may reallocate the skb head, after which PPPoE writes through the invalid pointer. Exploitation requires local low privileges and the PPPoE/team-device/GRE preconditions. News reporting dated 2026-09-18 claims active exploitation in connection with a CISA Known Exploited Vulnerabilities addition, although the supplied KEV digest itself says this CVE is not listed and the article excerpt does not explicitly name it. No public exploit code is recorded. EPSS is 0.1% with a flat trend, but reported exploitation takes precedence over that prediction.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS6th

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.2% chance of exploitation activity in the next 30 days, which ranks it in the 6th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

6 events over 11 days, from the signal feeds we watch.

2026-08-21OpenVAS check added
2026-08-19Record updated
2026-08-17Record updated
2026-08-13Record updated
2026-08-10Publishedrecord updated

Affected products

Linuxoss-projectaka the linux kernel
- LinuxOSOn-premOperating Systems / linux-distro

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Scored 7.8 by NVD.

How it is reached

Attack Vector LocalRequires local access to the vulnerable system (e.g. local login, malicious file)
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required LowRequires basic user-level privileges
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

Confidentiality HighTotal information disclosure — all data in the component is compromised
Integrity HighTotal loss of integrity — attacker can modify any data in the component
Availability HighTotal denial of service — the component is completely unavailable

Sources

References in the record

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In the news

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