KEVWire

Security intelligence, with context.

Response snapshot Oct 27, 2026, 01:23 UTC

Back to the wire
Permalink
VulnerabilityCVE-2026-98441

Linux kernel: net/sched: act_ct: avoid modifying shared unconfirmed ct entry

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: avoid modifying shared unconfirmed ct entry In a case where skb with an unconfirmed ct entry gets cloned, we may end up processing both again but with different sets of extensions. The series of events: 1.

At a glance

Exploited
Not known
Severity
7.8 High (CVSS 3.1)
Chance of exploitation
0.1% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-98441 (opens a new tab)

What happened

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_ct: avoid modifying shared unconfirmed ct entry

In a case where skb with an unconfirmed ct entry gets cloned, we may end up processing both again but with different sets of extensions.

The series of events:

Continue reading

1. The first clone wants to commit and runs the helpers wiring up the extension pointer into the expectation list. 2. Then it looses the confirmation keeping the entry unconfirmed. 3. Second clone now wants to commit labels or run NAT and adds the new extension for that breaking the pointer in the expectation list causing UAF on the destruction path later.

While this is possible to trigger, there should be no practical network pipeline where we need to process both clones without modifications in the same zone. So, let's just reset the entry in case for some reason we got an skb with a shared one. This doesn't affect any known use cases, but avoids any potential problems with sharing and modification of the unconfirmed ct entry.

Unlike openvswitch module, act_ct allows for NAT without commit. Changing that would be a uAPI break. So, act_ct needs to reset on NAT regardless of the commit flag to avoid reallocation of the extension space. This, however, doesn't really change the picture for sensible networking cases as there should be no need to run the same packet twice (before and after the clone) through conntrack without packet header or zone changes and without commit.

The fixes tag points to the introduction of helpers, since that's the main UAF trigger for the sharing.

Scores and how they were measured

CVSS base severity

7.8

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.1%

Scored Percentile 2.8%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-98441 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-98441, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 24). Linux kernel: net/sched: act_ct: avoid modifying shared unconfirmed ct entry (CVE-2026-98441). https://kevwire.com/record/CVE-2026-98441

MLA

"Linux kernel: net/sched: act_ct: avoid modifying shared unconfirmed ct entry (CVE-2026-98441)." KEVWire, 24 Oct. 2026, kevwire.com/record/CVE-2026-98441.

Chicago

KEVWire. "Linux kernel: net/sched: act_ct: avoid modifying shared unconfirmed ct entry (CVE-2026-98441)." Last modified October 24, 2026. https://kevwire.com/record/CVE-2026-98441.

Evidence summary (plain text)

Linux kernel: net/sched: act_ct: avoid modifying shared unconfirmed ct entry (Oct 18, 2026).
In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_ct: avoid modifying shared unconfirmed ct entry

In a case where skb with an unconfirmed ct entry gets cloned, we may
end up processing both again but with different sets of extensions.

The series of events:

 1. The first clone wants to commit and runs the helpers wiring up
    the extension pointer into the expectation list.
 2. Then it looses the confirmation keeping the entry unconfirmed.
 3. Second clone now wants to commit labels or run NAT and adds the
    new extension for that breaking the pointer in the expectation
    list causing UAF on the destruction path later.

While this is possible to trigger, there should be no practical
network pipeline where we need to process both clones without
modifications in the same zone.  So, let's just reset the entry in
case for some reason we got an skb with a shared one.  This doesn't
affect any known use cases, but avoids any potential problems with
sharing and modification of the unconfirmed ct entry.

Unlike openvswitch module, act_ct allows for NAT without commit.
Changing that would be a uAPI break.  So, act_ct needs to reset on NAT
regardless of the commit flag to avoid reallocation of the extension
space.  This, however, doesn't really change the picture for sensible
networking cases as there should be no need to run the same packet
twice (before and after the clone) through conntrack without packet
header or zone changes and without commit.

The fixes tag points to the introduction of helpers, since that's the
main UAF trigger for the sharing.
CVSS 7.8 (version 3.1; evidence as of Oct 24, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-98441).
EPSS 0.1% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-98441&date=2026-10-26).
Sources:
NVD CVE-2026-98441: https://nvd.nist.gov/vuln/detail/CVE-2026-98441
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=4500
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-98441&date=2026-10-26
Record ID: CVE-2026-98441.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

Record JSON

Your account

Email alerts

Email alerts are not available yet. To follow your stack today, use its RSS feed, which honors your filters, or connect an AI agent through the API.

Suggest an improvement

Ideas, missing sources, corrections, and bugs are all welcome. No account needed. Suggestions are reviewed by a person before anything changes.

Record details

Record detail