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NVD / CVE Program· CNA Linux

CVE-2026-31423: net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()

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: 0.12% (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 17c1b9807b8a67d676b6dcf749ee932ebaa7f568, 25b6821884713a31e2b49fb67b0ebd765b33e0a9, 4576100b8cd03118267513cafacde164b498b322; azl3 kernel 6.6.130.1-3 on Azure Linux 3.0 6.6.134.1-2.

Low priority for now. Upgrade to Linux Linux 17c1b9807b8a67d676b6dcf749ee932ebaa7f568, 25b6821884713a31e2b49fb67b0ebd765b33e0a9, 4576100b8cd03118267513cafacde164b498b322; azl3 kernel 6.6.130.1-3 on Azure Linux 3.0 6.6.134.1-2 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: sch_hfsc: fix divide-by-zero in rtsc_min() m2sm() converts a u32 slope to a u64 scaled value. For large inputs (e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores the difference of two such u64 values in a u32 variable `dsm` and uses it as a divisor. When the difference is exactly 2^32 the truncation yields zero, causing a divide-by-zero oops in the concave-curve intersection path: Oops: divide error: 0000 RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601) Call Trace: init_ed (net/sched/sch_hfsc.c:629) hfsc_enqueue (net/sched/sch_hfsc.c:1569) [...] Widen `dsm` to u64 and replace do_div() with div64_u64() so the full difference is preserved.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Apr 13, 2026
Updated
Nov 5, 2026
EPSS
0.1% · 1th 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 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

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-2026-31423

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

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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.

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 kernel2.6.12.1 and later · before 5.10.253
  • linux linux kernel5.11 and later · before 5.15.203
  • linux linux kernel5.16 and later · before 6.1.168
  • linux linux kernel6.2 and later · before 6.6.134
  • linux linux kernel6.7 and later · before 6.12.81
  • linux linux kernel6.13 and later · before 6.18.22
  • linux linux kernel6.19 and later · before 6.19.12
  • linux linux kernel2.6.12
  • linux linux kernel7.0

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

    • 2.6.12affected
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before ad8e8fec40290a8c8cf145c0deaadf76f80c5163affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before ab1ff5890c7354afc7be56502fcfbd61f3b7ae4faffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 25b6821884713a31e2b49fb67b0ebd765b33e0a9affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before c56f78614e7781aaceca9bd3cb2128bf7d45c3bdaffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before b9e6431cbea8bb1fae8069ed099b4ee100499835affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 17c1b9807b8a67d676b6dcf749ee932ebaa7f568affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 4576100b8cd03118267513cafacde164b498b322affected · git
    • before 2.6.12not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.12-16.19.12-1

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-2026-31421Apr 13, 2026 · net/sched: cls_fw: fix NULL pointer dereference on shared blocks
    22Monitor
  • ← EarlierCVE-2026-31422Apr 13, 2026 · net/sched: cls_flow: fix NULL pointer dereference on shared blocks
    22Monitor
  • Later →CVE-2026-31424Apr 13, 2026 · netfilter: x_tables: restrict xt_check_match/xt_check_target extensions for NFPROTO_ARP
    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 Linux17c1b9807b8a67d676b6dcf749ee932ebaa7f568Vendor (CNA)
Linux Linux25b6821884713a31e2b49fb67b0ebd765b33e0a9Vendor (CNA)
Linux Linux4576100b8cd03118267513cafacde164b498b322Vendor (CNA)
Linux Linuxab1ff5890c7354afc7be56502fcfbd61f3b7ae4fVendor (CNA)
Linux Linuxad8e8fec40290a8c8cf145c0deaadf76f80c5163Vendor (CNA)
Linux Linuxb9e6431cbea8bb1fae8069ed099b4ee100499835Vendor (CNA)
Linux Linuxc56f78614e7781aaceca9bd3cb2128bf7d45c3bdVendor (CNA)
Linux Linuxd0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5Vendor (CNA)
azl3 kernel 6.6.130.1-3 on Azure Linux 3.06.6.134.1-2 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.170-1 · 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.

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-2026-3160311 days apartstaging: sm750fb: fix division by zero in ps_to_hz()
    22Monitor
  • CVE-2026-3160511 days apartfbdev: udlfb: avoid divide-by-zero on FBIOPUT_VSCREENINFO
    22Monitor
  • CVE-2026-3161811 days apartfbdev: tdfxfb: avoid divide-by-zero on FBIOPUT_VSCREENINFO
    22Monitor
  • CVE-2026-3176718 days apartdrm/i915/dsi: Don't do DSC horizontal timing adjustments in command mode
    22Monitor
  • CVE-2026-3177018 days aparthwmon: (occ) Fix division by zero in occ_show_power_1()
    22Monitor
  • CVE-2026-2337919 days apartnet/sched: ets: fix divide by zero in the offload path
    22Monitor

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-369 · Divide By Zero

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 (10 more)

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

All records