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CVE-2026-98811

net/sched: cls_api: reclaim an empty proto on the error path

Products / packages Linux

Published

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Severity and exploitation

Not in CISA KEVNo CVSS score

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 23:05:32 UTC

Severity

unknown

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Fix status not established

No structured fix or guidance is available here. Check the latest publisher advisory.

What this means

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

Source excerpt · Linux

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

Linux · Linux

Linux

7 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

8b64678e0af8f4d62a40149baedebe78503a5255 → before 0f005c9b8b2e4c018e598cbaf490f27bebfd3d1f

git versions

8b64678e0af8f4d62a40149baedebe78503a5255 → before 00ad96ee96760d2f12f8c4b3a43f6c6b742c452f

git versions

8b64678e0af8f4d62a40149baedebe78503a5255 → before 0fc74e7d97d232095ce64cb45d25f0919df7ad4a

git versions

8b64678e0af8f4d62a40149baedebe78503a5255 → before 315e4fe65cf02ef052de5e6298c3088e448b7517

git versions

8b64678e0af8f4d62a40149baedebe78503a5255 → before ebc9611ab154c0cd9f1320e2a73f5e936d7535a9

git versions

8b64678e0af8f4d62a40149baedebe78503a5255 → before 570141625d212fbbcffb9665cb45c0f04610e61a

git versions

8b64678e0af8f4d62a40149baedebe78503a5255 → before 0bb8eab29b55045281a4963d4557f2776cdf8cfa

git versions

unaffected

unknown

Other versions: unaffected

Linux · Linux

Linux

9 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

5.1

unaffected

0 → before 5.1

semver versions

5.15.224 → through 5.15.*

semver versions

6.1.191 → through 6.1.*

semver versions

6.6.160 → through 6.6.*

semver versions

6.12.113 → through 6.12.*

semver versions

6.18.56 → through 6.18.*

semver versions

7.2.10 → through 7.2.*

semver versions

7.3 → through *

original_commit_for_fix versions

unknown

Other versions: affected

Automatic dependency matching is unavailable for this record. Use the product evidence and publisher’s instructions to check your installation.

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

No structured fix or remediation guidance is available here. Check the full source description and vendor’s latest advisory for a patch or workaround; do not assume another version is safe.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

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

net/sched: cls_api: reclaim an empty proto on the error path

Two racing tc filter add requests on the same chain/prio of an unlocked classifier both run change() on the shared proto and both can fail: the winner's tcf_chain_tp_delete_empty() attempt gives up because the loser's handle is still in the idr, and the loser's error path drops only its own reference without a second reclamation attempt. The empty proto stays linked in the chain, holding the chain reference, a block reference and the classifier module reference until the chain or block is torn down.

Reclaim the proto on the error path of any failed request that holds a proto reference. The reclamation is emptiness-gated: tcf_chain_tp_delete_empty() unlinks the proto only when delete_empty() admits it is empty, so a live shared proto is never unlinked. A proto the request created is reclaimed unconditionally - it is the only owner, so marking it for deletion is safe even without a delete_empty callback. Classifiers without one (the check marks the proto unconditionally) are rtnl-serialized, so the raced window this guard closes cannot arise for them.

This is a follow-up to commit d4e359b3608a ("net/sched: cls_api: fix teardown of an adopted proto on insert-race loss"), which stopped the loser of the insert race from unlinking the winner's live proto but left the empty-proto residual in place.

Conditions to recreate:

  • CONFIG_NET_CLS_FLOWER=y; veth pair
  • tc qdisc add dev veth0 ingress
  • two concurrent tc filter add dev veth0 ingress protocol ip pref 1 flower skip_sw ... action drop (both fail in fl_hw_replace_filter after publishing their handle in the idr); repeat in a loop
  • an empty flower tp stays linked after both requests fail; visible as a bare filter protocol ip pref 1 flower chain 0 header in tc filter show with no filter entries
  • CAP_NET_ADMIN (namespace-local via unshare -Urn suffices)

References

7 sources
git.kernel.org/stable/c/0f005c9b8b2e4c018e598cbaf490f27bebfd3d1f
Source referenceLinux
git.kernel.org/stable/c/00ad96ee96760d2f12f8c4b3a43f6c6b742c452f
Source referenceLinux
git.kernel.org/stable/c/0fc74e7d97d232095ce64cb45d25f0919df7ad4a
Source referenceLinux
git.kernel.org/stable/c/315e4fe65cf02ef052de5e6298c3088e448b7517
Source referenceLinux
git.kernel.org/stable/c/ebc9611ab154c0cd9f1320e2a73f5e936d7535a9
Source referenceLinux
git.kernel.org/stable/c/570141625d212fbbcffb9665cb45c0f04610e61a
Source referenceLinux
View 1 more references
git.kernel.org/stable/c/0bb8eab29b55045281a4963d4557f2776cdf8cfa
Source referenceLinux

Inside the record

Evidence available

Package identity · not supplied
Version evidence
Remediation guidance · not supplied
Weakness classification · not supplied
Additional publishers · not supplied

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-98811

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Environment requirements

These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.

Linux · platform conditions

Any condition may hold

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 5.15.224

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 6.1.191

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 6.6.160

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 6.12.113

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 6.18.56

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 7.2.10

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.1

Before: 7.3

Applicability preview
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  {
    "nodes": [
      {
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        "cpeMatch": [
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            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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          {
            "vulnerable": true,
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Contributing organizations · 1
Linux

Assigning organization

2026-10-30

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes
No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.