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CVE Record

CVE-2023-3609: Use-after-free in Linux kernel's net/sched: cls_u32 component

A use-after-free vulnerability in the Linux kernel's net/sched: cls_u32 component can be exploited to achieve local privilege escalation. If tcf_change_indev() fails, u32_set_parms() will immediately return an error after incrementing or decrementing the reference counter in tcf_bind_filter(). If an attacker can control the reference counter and set it to zero, they can cause the reference to be freed, leading to a use-after-free vulnerability. We recommend upgrading past commit 04c55383fa5689357bcdd2c8036725a55ed632bc.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in the Linux kernel’s traffic-control classifier can let a user who already has limited local access gain full system privileges. Successful exploitation could expose data, alter systems, or cause outages. Internet reachability alone is insufficient; the attacker needs local low-privilege access.

Executive priority

Prioritize remediation as high, especially for multi-user, shared, or already exposed systems. This is not evidenced as an internet-direct or actively exploited issue, but successful privilege escalation can convert a limited foothold into complete host compromise. Use normal emergency kernel-change controls and verify the running kernel afterward.

Technical view

CVE-2023-3609 is a use-after-free in net/sched/cls_u32. When tcf_change_indev() fails, u32_set_parms() returns after tcf_bind_filter() changes a reference count. If an attacker drives that count to zero, the freed reference may be reused. CVSS 3.1 rates it 7.8: local, low complexity, low privileges, no user interaction.

Likely exposure

Exposure is most likely on systems running a vulnerable Linux kernel where untrusted or compromised low-privilege users can reach the affected traffic-control functionality. The bundle’s version data is ambiguous and includes a default status of unaffected, so determine exposure through kernel build provenance and vendor guidance rather than release-number matching alone.

Exploitation context

The supplied sources characterize this as local privilege escalation. CISA KEV status is false, and the bundle provides no cited evidence of active exploitation. Treat compromised accounts, shared hosts, and other environments allowing low-privilege local access as higher-risk, without assuming remote unauthenticated exploitation.

Researcher notes

CWE-416 applies. The key failure path combines reference-count modification in tcf_bind_filter(), failure in tcf_change_indev(), and early return from u32_set_parms(). The supplied affected-version list is internally difficult to interpret because it includes the recommended fix commit while stating a default unaffected status. Validate fixes by commit inclusion or vendor backport documentation.

Mitigation direction

  • Upgrade to a kernel containing or succeeding commit 04c55383fa5689357bcdd2c8036725a55ed632bc.
  • Apply the supported Linux distribution or appliance vendor’s security update.
  • Prioritize shared systems and hosts permitting untrusted local access.
  • Reboot where required so the corrected kernel is actually running.

Validation and detection

  • Inventory running kernel builds, not only installed kernel packages.
  • Confirm each build contains the referenced upstream fix or an approved vendor backport.
  • Check vendor advisories for product-specific affected and corrected versions.
  • Verify systems booted into the updated kernel after maintenance.
  • Reassess hosts allowing untrusted or compromised low-privilege local access.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-416: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2023-3609 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
2ADP providers
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Google

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2023-3609Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxKernelkernel, 4.14.0, 4.15.0, 4.20.0, 5.5.0, 5.11.0, 5.16.0, 6.2.0, 6.4.0, 04c55383fa5689357bcdd2c8036725a55ed632bcunaffected
Weakness

CWE details

CWE-416

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.