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NVD / CVE Program· CNA Linux

CVE-2026-74583: net/sched: cls_route: fix fastmap use-after-free on filter

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: 0.11% (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 0e7a8cf8895b06d07c7311f028eba16ad742b9bc, 47d7f7051253bdc02b1d245d87e38f16d31a74df, 5ec9001be6d0eb527251125632ec8fe88278897f; azl3 kernel 6.6.150.1-1 on Azure Linux 3.0 6.6.152.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0e7a8cf8895b06d07c7311f028eba16ad742b9bc, 47d7f7051253bdc02b1d245d87e38f16d31a74df, 5ec9001be6d0eb527251125632ec8fe88278897f; azl3 kernel 6.6.150.1-1 on Azure Linux 3.0 6.6.152.1-1 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_route: fix fastmap use-after-free on filter The route4 classifier maintains a 16-slot fastmap cache that stores raw struct route4_filter pointers indexed by (id, iif). The reader (route4_classify) populates this cache via route4_set_fastmap() for every classified packet that hits a filter. The writer (route4_delete, route4_change) clears the cache via route4_reset_fastmap() before RCU-deferred kfree of the filter. This creates a UAF race: 1. Reader walks the RCU-protected bucket chain, finds filter f 2. Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work() 3. Reader calls route4_set_fastmap() and writes f into the cache *after* the writer's reset, caching a pointer about to be freed 4. After the RCU grace period, kfree(f) executes 5. Next classified packet on the same (id, iif) tuple hits the stale fastmap entry and reads f->res from freed memory Reproduced with an mdelay(100) accelerator in route4_set_fastmap() and a concurrent add/delete stress test (provided by both zdi and Santosh). Both triggered KASAN slab-use-after-free reports in the route4 fastmap paths. Fix: Introduce a per-filter boolean dying flag to suppress stale fastmap republishing by in-flight readers.

HighCVSS 7.8 · v3.1—Proof of concept Fix available
Published
Aug 21, 2026
Updated
Oct 16, 2026
EPSS
0.1% · 1th percentile
CWE
—

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 · 0.1%

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

    • 3.18affected
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before 7897198b26445b4009a057bda1986b94a99e5d5faffected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before 820f083c294ad6d319c02a7d43294f2ed2565139affected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before 5ec9001be6d0eb527251125632ec8fe88278897faffected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before b969984b2bdc85d721ce4047cd270cd37ec705a2affected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before a17f636c9330eac879822ce29f998e5abd1b72c1affected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before 0e7a8cf8895b06d07c7311f028eba16ad742b9bcaffected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before ae9aff87025219005a2d16b4fe83d6f24643e50daffected · git
    • 1109c00547fc66df45b9ff923544be4c1e1bec13 and later · before 47d7f7051253bdc02b1d245d87e38f16d31a74dfaffected · git
    • before 3.18not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.174.1.el8_104.18.0-553.174.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10
AlmaLinux:8kernel-rt-modulesbefore 4.18.0-553.174.1.rt7.515.el8_104.18.0-553.174.1.rt7.515.el8_10

+66

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-2026-74581Aug 21, 2026 · net: ipv6: clear suppressed fib6 rule result
    39Monitor
  • ← EarlierCVE-2026-74582Aug 21, 2026 · packet: use consistent hard_header_len in non-ring send paths
    31Monitor
  • Later →CVE-2026-74584Aug 22, 2026 · RDMA/bnxt_re: zero shared page before exposing to userspace
    28Monitor

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 Linux0e7a8cf8895b06d07c7311f028eba16ad742b9bcVendor (CNA)
Linux Linux47d7f7051253bdc02b1d245d87e38f16d31a74dfVendor (CNA)
Linux Linux5ec9001be6d0eb527251125632ec8fe88278897fVendor (CNA)
Linux Linux7897198b26445b4009a057bda1986b94a99e5d5fVendor (CNA)
Linux Linux820f083c294ad6d319c02a7d43294f2ed2565139Vendor (CNA)
Linux Linuxa17f636c9330eac879822ce29f998e5abd1b72c1Vendor (CNA)
Linux Linuxae9aff87025219005a2d16b4fe83d6f24643e50dVendor (CNA)
Linux Linuxb969984b2bdc85d721ce4047cd270cd37ec705a2Vendor (CNA)
azl3 kernel 6.6.150.1-1 on Azure Linux 3.06.6.152.1-1 · Release NotesMicrosoft (MSRC)
almalinux:bpftool4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.174.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.174.1.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)
red hat:bpftool0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-abi-stablelists0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-core0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-core0:4.18.0-553.174.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage 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 ×1

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:02026-11-02

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 PoC+72 d
  3. TodayNov 8, 2026+79 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

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)

—

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.

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

Change log

  1. Exploit maturitynone → poc
  2. SSVC exploitation— → none
  3. 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