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NVD / CVE Program· CNA Linux

CVE-2026-68138: net/sched: serialize qdisc_rtab_list against concurrent get/put

Noroxi assessment

Priority: Monitor (action score 31/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.22% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 1b050d09dd1a0ddae83bf012cf4956b7a960235f, 4131dd0b6f67acddd616ed7c244e1d3eedd46e7b, 6e0241f6cbb149d926ee8efee2c734fea71452cf; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1b050d09dd1a0ddae83bf012cf4956b7a960235f, 4131dd0b6f67acddd616ed7c244e1d3eedd46e7b, 6e0241f6cbb149d926ee8efee2c734fea71452cf; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1 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: serialize qdisc_rtab_list against concurrent get/put qdisc_get_rtab() and qdisc_put_rtab() mutate the process-global singly linked list qdisc_rtab_list and a plain non-atomic 'int refcnt' with no lock. This was only safe because every caller historically held the RTNL mutex, which serialized all rate-table lookups, inserts and frees. That invariant no longer holds. cls_flower sets TCF_PROTO_OPS_DOIT_UNLOCKED, so tc_new_tfilter() keeps rtnl_held == false for it and sets TCA_ACT_FLAGS_NO_RTNL. That flag propagates through tcf_exts_validate_ex() -> tcf_action_init() -> tcf_action_init_1() -> tcf_police_init(), which calls qdisc_get_rtab()/qdisc_put_rtab() with the RTNL mutex NOT held. Two RTM_NEWTFILTER requests on different CPUs, each adding a flower filter with a police action carrying the same rate, then race on qdisc_rtab_list and on the non-atomic refcnt, leading to a use-after-free / double-free of the kmalloc-2k struct qdisc_rate_table. qdisc_rtab_list is a single global (not per-netns), so the corrupted object is shared system-wide. BUG: KASAN: slab-use-after-free in qdisc_put_rtab+0x12f/0x160 qdisc_put_rtab+0x12f/0x160 tcf_police_init+0xda9/0x1590 tcf_action_init_1+0x460/0x6b0 tcf_action_init+0x439/0xa40 tcf_exts_validate_ex+0x42d/0x550 fl_change+0xddd/0x7da0 tc_new_tfilter+0xaa7/0x2420 rtnetlink_rcv_msg+0x95e/0xe90 which belongs to the cache kmalloc-2k of size 2048 Protect qdisc_rtab_list and the refcount with a dedicated spinlock. The (sleeping, GFP_KERNEL) allocation in qdisc_get_rtab() is performed before taking the lock; if a concurrent inserter added an identical table in the meantime the freshly allocated one is freed under the lock, so no duplicate is leaked. qdisc_put_rtab() now decrements the refcount and unlinks under the same lock.

HighCVSS 7.8 · v3.1—Proof of concept Fix available
Published
Aug 10, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 12th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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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
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before 1b050d09dd1a0ddae83bf012cf4956b7a960235faffected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before 6e0241f6cbb149d926ee8efee2c734fea71452cfaffected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before f93c89392bd3b180b5b7abc6fdae8e3dd667a313affected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before 4131dd0b6f67acddd616ed7c244e1d3eedd46e7baffected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before d981098b76756ed71666a27518eeb69883657c43affected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before 8ddc2eb0d2da9c83f54f1e5720525b461b8480c4affected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before fb29e1b41052488ee3f2d115d4a870497ebd7f7daffected · git
    • 470502de5bdb1ed0def643a4458593a40b8f6b66 and later · before f43ee0c0730d6191629b5ee1ceae27b1ebfdc047affected · git
    • before 5.1not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.178.1.el8_104.18.0-553.178.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10
AlmaLinux:8kernel-rt-modulesbefore 4.18.0-553.178.1.rt7.519.el8_104.18.0-553.178.1.rt7.519.el8_10

+96

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-2026-68133Aug 10, 2026 · ice: fix PTP Call Trace during PTP release
    0Monitor
  • ← EarlierCVE-2026-68136Aug 10, 2026 · net: gro: fix double aggregation of flush-marked skbs
    39Monitor
  • Later →CVE-2026-68139Aug 10, 2026 · net/mlx5e: Use sender devcom for MPV master-up
    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 Linux1b050d09dd1a0ddae83bf012cf4956b7a960235fVendor (CNA)
Linux Linux4131dd0b6f67acddd616ed7c244e1d3eedd46e7bVendor (CNA)
Linux Linux6e0241f6cbb149d926ee8efee2c734fea71452cfVendor (CNA)
Linux Linux8ddc2eb0d2da9c83f54f1e5720525b461b8480c4Vendor (CNA)
Linux Linuxd981098b76756ed71666a27518eeb69883657c43Vendor (CNA)
Linux Linuxf43ee0c0730d6191629b5ee1ceae27b1ebfdc047Vendor (CNA)
Linux Linuxf93c89392bd3b180b5b7abc6fdae8e3dd667a313Vendor (CNA)
Linux Linuxfb29e1b41052488ee3f2d115d4a870497ebd7f7dVendor (CNA)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.06.6.157.1-1 · Release NotesMicrosoft (MSRC)
almalinux:bpftool4.18.0-553.178.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.178.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-core4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-core4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-devel4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-modules4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-modules-extra4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-devel4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-modules4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-modules-extra4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.107-1~deb12u1 · Debian:12Package registry (OSV)
rocky linux:kernel0:4.18.0-553.178.1.el8_10 · Rocky Linux:8Package registry (OSV)
rocky linux:kernel-rt0:4.18.0-553.178.1.rt7.519.el8_10 · Rocky Linux:8Package registry (OSV)
suse:kernel-livepatch-SLE16-RT_Update_016-160000.3.4 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-livepatch-SLE16-RT_Update_115-160000.1.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-livepatch-SLE16-RT_Update_125-160000.1.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-livepatch-SLE16-RT_Update_135-160000.1.1 · SUSE:Linux Micro 6.2Package registry (OSV)
suse:kernel-livepatch-SLE16-RT_Update_145-160000.1.1 · SUSE:Linux Micro 6.2Package registry (OSV)

+7

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×3

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:332026-08-11
Proof-of-concept repository on GitHubstars:02026-08-17
Proof-of-concept repository on GitHubstars:02026-08-17

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. First PoCsame day
  3. TodayNov 6, 2026+88 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.

  • CVE-2026-720645 days apartnet: mana: Sync page pool RX frags for CPU
    39Monitor
  • CVE-2026-6397822 days apartnet/handshake: Drain pending requests at net namespace exit
    39Monitor
  • CVE-2026-683290 days apartiommu/amd: Wait for completion instead of returning early in iommu_completion_wait()
    35Monitor
  • CVE-2026-645616 days apartKVM: x86: Check for invalid/obsolete root *after* making MMU pages available
    35Monitor
  • CVE-2026-682450 days apartdrm/amdgpu: fix lifetime issue of amdgpu_vm_get_task_info_pasid()
    31Monitor
  • CVE-2026-683820 days apartdrm/xe/guc: Hold device ref until queue teardown completes
    31Monitor

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSS vector

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

nvd-secondary

Attack context

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

ATT&CK techniques

—

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

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

All records