Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2025-21971: net_sched: Prevent creation of classes with TC_H_ROOT

Noroxi assessment

Priority: Monitor (action score 22/100)

  • 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: 0.22% (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 003d92c91cdb5a64b25a9a74cb8543aac9a8bb48, 0c3057a5a04d07120b3d0ec9c79568fceb9c921e, 5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 003d92c91cdb5a64b25a9a74cb8543aac9a8bb48, 0c3057a5a04d07120b3d0ec9c79568fceb9c921e, 5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7 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: Prevent creation of classes with TC_H_ROOT The function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a termination condition when traversing up the qdisc tree to update parent backlog counters. However, if a class is created with classid TC_H_ROOT, the traversal terminates prematurely at this class instead of reaching the actual root qdisc, causing parent statistics to be incorrectly maintained. In case of DRR, this could lead to a crash as reported by Mingi Cho. Prevent the creation of any Qdisc class with classid TC_H_ROOT (0xFFFFFFFF) across all qdisc types, as suggested by Jamal.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Apr 1, 2025
Updated
Oct 15, 2026
EPSS
0.2% · 13th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 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
5.5
CNA · Linux
7.8
2.3 point gap

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

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

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-21971

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

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.

We use this product, ask for help

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.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.26 and later · before 5.4.292
  • linux linux kernel5.5 and later · before 5.10.236
  • linux linux kernel5.11 and later · before 5.15.180
  • linux linux kernel5.16 and later · before 6.1.132
  • linux linux kernel6.2 and later · before 6.6.84
  • linux linux kernel6.7 and later · before 6.12.20
  • linux linux kernel6.13 and later · before 6.13.8
  • linux linux kernel2.6.25
  • linux linux kernel6.14

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

    • 2.6.25affected
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before e05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4caffected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before 7a82fe67a9f4d7123d8e5ba8f0f0806c28695006affected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before 003d92c91cdb5a64b25a9a74cb8543aac9a8bb48affected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before e5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7affected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before 78533c4a29ac3aeddce4b481770beaaa4f3bfb67affected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before 5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7affected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before 94edfdfb9505ab608e86599d1d1e38c83816fc1caffected · git
    • 066a3b5b2346febf9a655b444567b7138e3bb939 and later · before 0c3057a5a04d07120b3d0ec9c79568fceb9c921eaffected · git
    • before 2.6.25not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.133-16.1.133-1
Debian:13linuxbefore 6.12.20-16.12.20-1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-64kbbefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-default-basebefore 5.3.18-150300.59.218.1.150300.18.130.15.3.18-150300.59.218.1.150300.18.130.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-docsbefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-obs-buildbefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-preemptbefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-sourcebefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-symsbefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSkernel-64kbbefore 5.14.21-150400.24.173.15.14.21-150400.24.173.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSkernel-docsbefore 5.14.21-150400.24.173.15.14.21-150400.24.173.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSkernel-obs-buildbefore 5.14.21-150400.24.173.15.14.21-150400.24.173.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSkernel-sourcebefore 5.14.21-150400.24.173.15.14.21-150400.24.173.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSkernel-symsbefore 5.14.21-150400.24.173.15.14.21-150400.24.173.1
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSkernel-64kbbefore 5.14.21-150500.55.121.25.14.21-150500.55.121.2
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSkernel-docsbefore 5.14.21-150500.55.121.15.14.21-150500.55.121.1
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSkernel-obs-buildbefore 5.14.21-150500.55.121.15.14.21-150500.55.121.1
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSkernel-symsbefore 5.14.21-150500.55.121.15.14.21-150500.55.121.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_60before 18-2.118-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_61before 17-2.117-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_62before 17-2.117-2.1
SUSE:Linux Enterprise Live Patching 15 SP3kernel-defaultbefore 5.3.18-150300.59.218.15.3.18-150300.59.218.1
SUSE:Linux Enterprise Live Patching 15 SP3kernel-livepatch-SLE15-SP3_Update_48before 19-150300.2.119-150300.2.1
SUSE:Linux Enterprise Live Patching 15 SP3kernel-livepatch-SLE15-SP3_Update_49before 18-150300.2.118-150300.2.1

+54

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-21969Apr 1, 2025 · Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd
    31Monitor
  • ← EarlierCVE-2025-21970Apr 1, 2025 · net/mlx5: Bridge, fix the crash caused by LAG state check
    22Monitor
  • Later →CVE-2025-21972Apr 1, 2025 · net: mctp: unshare packets when reassembling
    22Monitor

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 Linux003d92c91cdb5a64b25a9a74cb8543aac9a8bb48Vendor (CNA)
Linux Linux0c3057a5a04d07120b3d0ec9c79568fceb9c921eVendor (CNA)
Linux Linux5c3ca9cb48b51bd72bf76b8b05e24f3cd53db5e7Vendor (CNA)
Linux Linux78533c4a29ac3aeddce4b481770beaaa4f3bfb67Vendor (CNA)
Linux Linux7a82fe67a9f4d7123d8e5ba8f0f0806c28695006Vendor (CNA)
Linux Linux94edfdfb9505ab608e86599d1d1e38c83816fc1cVendor (CNA)
Linux Linuxe05d9938b1b0ac40b6054cc5fa0ccbd9afd5ed4cVendor (CNA)
Linux Linuxe5ee00607bbfc97ef1526ea95b6b2458ac9e7cb7Vendor (CNA)
debian:linux6.1.133-1 · Debian:12Package registry (OSV)
suse:kernel-64kb5.14.21-150400.24.173.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSPackage registry (OSV)
suse:kernel-default3.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-default-base5.14.21-150400.24.173.1.150400.24.88.1 · SUSE:Linux Enterprise Micro 5.3Package registry (OSV)
suse:kernel-docs3.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-ec23.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-livepatch-SLE15-SP4_Update_431-150400.9.3.1 · SUSE:Linux Enterprise Live Patching 15 SP4Package registry (OSV)
suse:kernel-obs-build5.14.21-150400.24.173.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSPackage registry (OSV)
suse:kernel-source3.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-syms3.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-trace3.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-xen3.0.101-108.189.1 · SUSE:Linux Enterprise Server 11 SP4 LTSS EXTREME COREPackage registry (OSV)
suse:kernel-zfcpdump5.14.21-150400.24.173.1 · SUSE:Linux Enterprise Server 15 SP4-LTSSPackage 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.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

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-2026-31448386 days apartext4: avoid infinite loops caused by residual data
    37Monitor
  • CVE-2026-63889474 days apartscsi: scsi_transport_fc: Widen FPIN pname walker counter to u32
    32Monitor
  • CVE-2026-52933449 days apartio_uring/poll: fix signed comparison in io_poll_get_ownership()
    31Monitor
  • CVE-2026-23451367 days apartbonding: prevent potential infinite loop in bond_header_parse()
    30Monitor
  • CVE-2026-31552388 days apartwifi: wlcore: Return -ENOMEM instead of -EAGAIN if there is not enough headroom
    30Monitor
  • CVE-2026-46052421 days apartceph: only d_add() negative dentries when they are unhashed
    30Monitor

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

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

Weakness class (CWE)

CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')

CVSS vector

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

nvd-primary

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

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

References

Show all references (9 more)

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

All records