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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-98811: net/sched: cls_api: reclaim an empty proto on the error path

—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Fixed version: Linux Linux 00ad96ee96760d2f12f8c4b3a43f6c6b742c452f, 0bb8eab29b55045281a4963d4557f2776cdf8cfa, 0f005c9b8b2e4c018e598cbaf490f27bebfd3d1f; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 6.6.161.1-1.

Low priority for now. Upgrade to Linux Linux 00ad96ee96760d2f12f8c4b3a43f6c6b742c452f, 0bb8eab29b55045281a4963d4557f2776cdf8cfa, 0f005c9b8b2e4c018e598cbaf490f27bebfd3d1f; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 6.6.161.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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)

Published
Oct 18, 2026
Updated
Oct 30, 2026
EPSS
0.1% · 7th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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Noroxi analysis

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.1affected
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before 0f005c9b8b2e4c018e598cbaf490f27bebfd3d1faffected · git
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before 00ad96ee96760d2f12f8c4b3a43f6c6b742c452faffected · git
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before 0fc74e7d97d232095ce64cb45d25f0919df7ad4aaffected · git
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before 315e4fe65cf02ef052de5e6298c3088e448b7517affected · git
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before ebc9611ab154c0cd9f1320e2a73f5e936d7535a9affected · git
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before 570141625d212fbbcffb9665cb45c0f04610e61aaffected · git
    • 8b64678e0af8f4d62a40149baedebe78503a5255 and later · before 0bb8eab29b55045281a4963d4557f2776cdf8cfaaffected · git
    • before 5.1not affected · semver
    • 5.15.224 and later · up to and including 5.15.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:12linux-6.12before 6.12.113-1~deb12u16.12.113-1~deb12u1
Debian:13linuxbefore 6.12.113-16.12.113-1
Debian:14linuxbefore 7.2.10-17.2.10-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-98809Oct 18, 2026 · Bluetooth: hci_sync: don't drain cmd_sync backlog on unregister
    0Monitor
  • ← EarlierCVE-2026-98810Oct 18, 2026 · wifi: mac80211: fix slab-out-of-bounds read in ieee80211_monitor_select_queue()
    0Monitor
  • Later →CVE-2026-98812Oct 18, 2026 · net/mctp: publish the mctp_dev only after it is initialised
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux00ad96ee96760d2f12f8c4b3a43f6c6b742c452fVendor (CNA)
Linux Linux0bb8eab29b55045281a4963d4557f2776cdf8cfaVendor (CNA)
Linux Linux0f005c9b8b2e4c018e598cbaf490f27bebfd3d1fVendor (CNA)
Linux Linux0fc74e7d97d232095ce64cb45d25f0919df7ad4aVendor (CNA)
Linux Linux315e4fe65cf02ef052de5e6298c3088e448b7517Vendor (CNA)
Linux Linux570141625d212fbbcffb9665cb45c0f04610e61aVendor (CNA)
Linux Linuxebc9611ab154c0cd9f1320e2a73f5e936d7535a9Vendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.159.1-1 on Azure Linux 3.06.6.161.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.12.113-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.113-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 12, 2026+25 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

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References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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