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CVE Record

CVE-2024-35855: mlxsw: spectrum_acl_tcam: Fix possible use-after-free during activity update

In the Linux kernel, the following vulnerability has been resolved: mlxsw: spectrum_acl_tcam: Fix possible use-after-free during activity update The rule activity update delayed work periodically traverses the list of configured rules and queries their activity from the device. As part of this task it accesses the entry pointed by 'ventry->entry', but this entry can be changed concurrently by the rehash delayed work, leading to a use-after-free [1]. Fix by closing the race and perform the activity query under the 'vregion->lock' mutex. [1] BUG: KASAN: slab-use-after-free in mlxsw_sp_acl_tcam_flower_rule_activity_get+0x121/0x140 Read of size 8 at addr ffff8881054ed808 by task kworker/0:18/181 CPU: 0 PID: 181 Comm: kworker/0:18 Not tainted 6.9.0-rc2-custom-00781-gd5ab772d32f7 #2 Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019 Workqueue: mlxsw_core mlxsw_sp_acl_rule_activity_update_work Call Trace: <TASK> dump_stack_lvl+0xc6/0x120 print_report+0xce/0x670 kasan_report+0xd7/0x110 mlxsw_sp_acl_tcam_flower_rule_activity_get+0x121/0x140 mlxsw_sp_acl_rule_activity_update_work+0x219/0x400 process_one_work+0x8eb/0x19b0 worker_thread+0x6c9/0xf70 kthread+0x2c9/0x3b0 ret_from_fork+0x4d/0x80 ret_from_fork_asm+0x1a/0x30 </TASK> Allocated by task 1039: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x8f/0xa0 __kmalloc+0x19c/0x360 mlxsw_sp_acl_tcam_entry_create+0x7b/0x1f0 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x30d/0xb50 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300 process_one_work+0x8eb/0x19b0 worker_thread+0x6c9/0xf70 kthread+0x2c9/0x3b0 ret_from_fork+0x4d/0x80 ret_from_fork_asm+0x1a/0x30 Freed by task 1039: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 poison_slab_object+0x102/0x170 __kasan_slab_free+0x14/0x30 kfree+0xc1/0x290 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x3d7/0xb50 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300 process_one_work+0x8eb/0x19b0 worker_thread+0x6c9/0xf70 kthread+0x2c9/0x3b0 ret_from_fork+0x4d/0x80 ret_from_fork_asm+0x1a/0x30

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A race condition in the Linux mlxsw driver can make background work access memory after it has been freed. It primarily matters to systems using Mellanox Spectrum switching hardware and ACL TCAM rules. A triggered failure could crash or compromise the kernel, but the supplied evidence does not establish real-world exploitation.

Executive priority

Treat as high priority for Mellanox Spectrum switching infrastructure using hardware ACLs because failure occurs in kernel context. Expedite inventory and vendor-kernel updates on exposed devices. Other Linux systems are unlikely to exercise this driver path, so validate applicability before initiating broad emergency remediation.

Technical view

The mlxsw Spectrum ACL activity worker dereferences ventry->entry while rehash work can concurrently replace and free that entry. KASAN observed a slab use-after-free during mlxsw_sp_acl_tcam_flower_rule_activity_get. The kernel fix serializes the activity query with rehash operations using the vregion->lock mutex.

Likely exposure

Exposure is concentrated in Linux systems using the mlxsw Spectrum ACL TCAM path, especially Mellanox Spectrum switches managing hardware ACL rules. The supplied affected-version data includes kernels through 6.9 and several stable-series releases, but it does not provide a clean universal version range. Distribution backports require separate verification.

Exploitation context

The supplied CVSS is 7.8 with local access, low privileges, low complexity, and potential confidentiality, integrity, and availability impact. The bundle marks the CVE as absent from KEV and provides no evidence of active exploitation or a public exploit. Practical exploitability beyond the demonstrated KASAN failure remains unconfirmed.

Researcher notes

The evidence demonstrates a concurrency flaw between ACL rule activity updates and virtual-region rehash work. KASAN reproduced an eight-byte read after free on a custom 6.9-rc2 kernel running Mellanox MSN3700 hardware. Locking closes the documented race. No CWE, reliable trigger conditions, exploit demonstration, or confirmed attack activity is supplied.

Mitigation direction

  • Update to a distribution or vendor kernel incorporating the applicable upstream stable fix.
  • Prioritize Mellanox Spectrum systems actively using mlxsw hardware ACL rules.
  • If patching is delayed, check vendor guidance; the supplied sources name no workaround.
  • Monitor relevant systems for kernel crashes or use-after-free diagnostics.

Validation and detection

  • Inventory kernel versions and identify systems using mlxsw Spectrum ACL TCAM functionality.
  • Map deployed kernels to vendor advisories and the applicable stable fix commit.
  • Verify the installed kernel changelog or source includes the vregion->lock activity-query fix.
  • After updating, test normal ACL changes and monitor kernel logs for memory-safety failures.
Prepared
Confidence
medium
Sources
10

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

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CVE-2024-35855 mapping review

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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
9Source links

SSVC decision data

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

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:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2024-35855Attack 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

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux2bffc5322fd8679e879cd6370881ee50cf141ada, 2bffc5322fd8679e879cd6370881ee50cf141ada, 2bffc5322fd8679e879cd6370881ee50cf141ada, 2bffc5322fd8679e879cd6370881ee50cf141ada, 2bffc5322fd8679e879cd6370881ee50cf141ada, 2bffc5322fd8679e879cd6370881ee50cf141ada, 2bffc5322fd8679e879cd6370881ee50cf141adaunaffected
LinuxLinux5.1, 0, 5.4.275, 5.10.216, 5.15.158, 6.1.90, 6.6.30, 6.8.9, 6.9affected
Weakness

CWE details

No CWE listed

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