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CVE Record

CVE-2024-46786: fscache: delete fscache_cookie_lru_timer when fscache exits to avoid UAF

In the Linux kernel, the following vulnerability has been resolved: fscache: delete fscache_cookie_lru_timer when fscache exits to avoid UAF The fscache_cookie_lru_timer is initialized when the fscache module is inserted, but is not deleted when the fscache module is removed. If timer_reduce() is called before removing the fscache module, the fscache_cookie_lru_timer will be added to the timer list of the current cpu. Afterwards, a use-after-free will be triggered in the softIRQ after removing the fscache module, as follows: ================================================================== BUG: unable to handle page fault for address: fffffbfff803c9e9 PF: supervisor read access in kernel mode PF: error_code(0x0000) - not-present page PGD 21ffea067 P4D 21ffea067 PUD 21ffe6067 PMD 110a7c067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G W 6.11.0-rc3 #855 Tainted: [W]=WARN RIP: 0010:__run_timer_base.part.0+0x254/0x8a0 Call Trace: <IRQ> tmigr_handle_remote_up+0x627/0x810 __walk_groups.isra.0+0x47/0x140 tmigr_handle_remote+0x1fa/0x2f0 handle_softirqs+0x180/0x590 irq_exit_rcu+0x84/0xb0 sysvec_apic_timer_interrupt+0x6e/0x90 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 RIP: 0010:default_idle+0xf/0x20 default_idle_call+0x38/0x60 do_idle+0x2b5/0x300 cpu_startup_entry+0x54/0x60 start_secondary+0x20d/0x280 common_startup_64+0x13e/0x148 </TASK> Modules linked in: [last unloaded: netfs] ================================================================== Therefore delete fscache_cookie_lru_timer when removing the fscahe module.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2024-46786 is a Linux kernel flaw in FS-Cache cleanup. A timer can remain active after the fscache module is removed, causing kernel use-after-free behavior and a crash. The public record does not show active exploitation or a CVSS score.

Executive priority

Patch in the normal kernel maintenance cycle, with faster handling for systems using FS-Cache or vendor products named by Siemens. There is no cited evidence of active exploitation, but kernel memory-safety bugs can cause outages and deserve tracked remediation.

Technical view

The fscache_cookie_lru_timer is initialized on fscache module insertion but was not deleted during module removal. If timer_reduce() queued the timer before removal, later softIRQ timer handling could access freed module state, triggering a kernel use-after-free. Stable kernel commits add timer deletion during fscache exit.

Likely exposure

Exposure is most relevant to systems running affected Linux kernels where FS-Cache or related netfs functionality is present. The source bundle lists affected Linux kernel versions including 5.17, 6.1.160, 6.6.51, 6.10.10, and 6.11. Product impact beyond Linux and the Siemens advisory is not detailed here.

Exploitation context

The provided sources describe a reproducible kernel fault condition during fscache module removal after timer activity. They do not claim remote exploitation, active attacks, privilege escalation, or inclusion in CISA KEV. Treat exploitability beyond denial-of-service style kernel instability as unproven from this bundle.

Researcher notes

The key condition is stale fscache_cookie_lru_timer state after fscache module exit. The bundle gives crash evidence and upstream stable commits, but lacks CVSS, CWE, complete distro mappings, exploitability analysis, and detailed Siemens affected-product context.

Mitigation direction

  • Update affected Linux kernels to versions containing the referenced stable commits.
  • Review vendor advisories for distribution-specific package names and fixed builds.
  • Prioritize systems using FS-Cache, netfs, or cache-backed network filesystems.
  • For Siemens environments, follow Siemens SSA-019113 product guidance.
  • Avoid relying on unverified workarounds not named by kernel or vendor sources.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded systems.
  • Check whether FS-Cache or netfs modules are present or loaded.
  • Map installed kernels against vendor fixed versions and stable commits.
  • Review crash logs for timer or fscache-related kernel oops signatures.
  • Confirm Siemens advisory applicability for managed industrial products.
Prepared
Confidence
medium
Sources
7

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-2024-46786 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
2ADP providers
6Source links

SSVC decision data

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

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
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux12bb21a29c19aae50cfad4e2bb5c943108f34a7d, 12bb21a29c19aae50cfad4e2bb5c943108f34a7d, 12bb21a29c19aae50cfad4e2bb5c943108f34a7d, 12bb21a29c19aae50cfad4e2bb5c943108f34a7dunaffected
LinuxLinux5.17, 0, 6.1.160, 6.6.51, 6.10.10, 6.11affected
Weakness

CWE details

No CWE listed

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