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

CVE-2026-99121: ipv4: avoid divide by zero in fib_rebalance

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: 0.18% (FIRST EPSS).
  • Fixed version: Linux Linux 0800c92ca5d1983df6843a5435299978901d1d02, 226a974054acbd892560bfa67f0ae8ffe271a736, 5046d2880fec7d49ebed2fd2866747ee1d06ad71; 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 Release Notes.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0800c92ca5d1983df6843a5435299978901d1d02, 226a974054acbd892560bfa67f0ae8ffe271a736, 5046d2880fec7d49ebed2fd2866747ee1d06ad71; 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 Release Notes 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: ipv4: avoid divide by zero in fib_rebalance fib_rebalance() computes the total eligible nexthop weight in one pass and programs upper bounds in a second pass. A concurrent change to ignore_routes_with_linkdown can make the first pass return zero while the second pass sees an eligible nexthop, resulting in division by zero. If the first pass reports a zero total, set each nexthop upper bound to -1 and skip the division. This matches the IPv6 fix in commit d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance") and preserves the lock-free rebalance path.

—No exploit Fix available
Published
Oct 28, 2026
Updated
Oct 30, 2026
EPSS
0.1% · 8th 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%

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

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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

    • 4.4affected
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before baf3a767b2845eb8e68f056ee4aa5b41b151e990affected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before f655a26490e705ec76a79db7f412847fda342b39affected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before 7c68f4de5090b17b63b9a0a3b01b3807e01a296aaffected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before 226a974054acbd892560bfa67f0ae8ffe271a736affected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before 0800c92ca5d1983df6843a5435299978901d1d02affected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before 5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8faffected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before d5520e815c4b1427104ce1428ee23821f2aa824daffected · git
    • 0e884c78ee19e902f300ed147083c28a0c6302f0 and later · before 5046d2880fec7d49ebed2fd2866747ee1d06ad71affected · git
    • before 4.4not 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:13linuxbefore 6.12.115-26.12.115-2

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-2026-99119Oct 28, 2026 · drm/amdgpu/userq: actually validate userq BOs
    0Monitor
  • ← EarlierCVE-2026-99120Oct 28, 2026 · KVM: x86/mmu: Cope with the SS bit being set in #NPF exit codes
    0Monitor
  • Later →CVE-2026-99122Oct 28, 2026 · vsock/vmci: validate packet source for connected sockets
    29Monitor

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 Linux0800c92ca5d1983df6843a5435299978901d1d02Vendor (CNA)
Linux Linux226a974054acbd892560bfa67f0ae8ffe271a736Vendor (CNA)
Linux Linux5046d2880fec7d49ebed2fd2866747ee1d06ad71Vendor (CNA)
Linux Linux5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8fVendor (CNA)
Linux Linux7c68f4de5090b17b63b9a0a3b01b3807e01a296aVendor (CNA)
Linux Linuxbaf3a767b2845eb8e68f056ee4aa5b41b151e990Vendor (CNA)
Linux Linuxd5520e815c4b1427104ce1428ee23821f2aa824dVendor (CNA)
Linux Linuxf655a26490e705ec76a79db7f412847fda342b39Vendor (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 3.0Release NotesMicrosoft (MSRC)
debian:linux6.12.115-2 · Debian:13Package 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 5, 2026+8 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).

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

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✗ → ✓

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