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CVE Record

CVE-2024-40995: net/sched: act_api: fix possible infinite loop in tcf_idr_check_alloc()

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_api: fix possible infinite loop in tcf_idr_check_alloc() syzbot found hanging tasks waiting on rtnl_lock [1] A reproducer is available in the syzbot bug. When a request to add multiple actions with the same index is sent, the second request will block forever on the first request. This holds rtnl_lock, and causes tasks to hang. Return -EAGAIN to prevent infinite looping, while keeping documented behavior. [1] INFO: task kworker/1:0:5088 blocked for more than 143 seconds. Not tainted 6.9.0-rc4-syzkaller-00173-g3cdb45594619 #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/1:0 state:D stack:23744 pid:5088 tgid:5088 ppid:2 flags:0x00004000 Workqueue: events_power_efficient reg_check_chans_work Call Trace: <TASK> context_switch kernel/sched/core.c:5409 [inline] __schedule+0xf15/0x5d00 kernel/sched/core.c:6746 __schedule_loop kernel/sched/core.c:6823 [inline] schedule+0xe7/0x350 kernel/sched/core.c:6838 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6895 __mutex_lock_common kernel/locking/mutex.c:684 [inline] __mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752 wiphy_lock include/net/cfg80211.h:5953 [inline] reg_leave_invalid_chans net/wireless/reg.c:2466 [inline] reg_check_chans_work+0x10a/0x10e0 net/wireless/reg.c:2481

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2024-40995 is a Linux kernel availability bug in traffic-control action handling. A malformed request adding multiple actions with the same index can cause an infinite wait while holding a major networking lock, leaving other kernel tasks blocked. Public sources show fixes in Linux stable commits, but no CVSS score or active exploitation evidence.

Executive priority

Handle through normal vulnerability remediation with elevated attention for high-availability Linux infrastructure and Siemens-managed environments. There is no cited active exploitation, but the bug can block kernel tasks and affect service reliability.

Technical view

The flaw is in net/sched act_api, specifically tcf_idr_check_alloc(). When duplicate action indexes are requested, the second allocation can block forever behind the first while rtnl_lock is held. The kernel fix returns -EAGAIN to avoid the infinite loop while preserving documented behavior.

Likely exposure

Exposure is most likely on Linux systems running affected kernel versions or vendor products that embed those kernels. The source bundle lists Linux affected versions and Siemens advisories, but it does not define required privileges, attack surface, or complete downstream product impact.

Exploitation context

The CVE record notes a syzbot reproducer and hanging tasks, not exploitation in the wild. KEV status is false in the provided bundle. Treat this as a denial-of-service style kernel reliability issue unless vendor guidance shows broader impact.

Researcher notes

The available evidence supports an availability impact in Linux net/sched action allocation. Key unknowns are privilege requirements, namespace constraints, and downstream product-specific exposure. Do not assume remote unauthenticated exploitability from the provided sources.

Mitigation direction

  • Upgrade to a kernel or vendor firmware containing the referenced stable fixes.
  • Check Debian LTS and Siemens advisories if those distributions or products are in use.
  • Prioritize internet-facing, multi-tenant, container-host, and operational technology Linux systems for review.
  • If no vendor update is available, monitor vendor guidance for supported mitigations.
  • Avoid deploying custom kernels without the net/sched act_api fix.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, containers hosts, and embedded systems.
  • Compare deployed kernels against vendor advisories and the referenced stable commits.
  • Check whether Siemens affected products named in advisories exist in the environment.
  • Review kernel logs for hung task reports involving rtnl_lock or traffic-control action handling.
  • Confirm patched systems run vendor-supported kernels after reboot.
Prepared
Confidence
medium
Sources
12

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

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CVE-2024-40995 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
3ADP providers
12Source 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

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux0190c1d452a91c38a3462abdd81752be1b9006a8, 0190c1d452a91c38a3462abdd81752be1b9006a8, 0190c1d452a91c38a3462abdd81752be1b9006a8, 0190c1d452a91c38a3462abdd81752be1b9006a8, 0190c1d452a91c38a3462abdd81752be1b9006a8, 0190c1d452a91c38a3462abdd81752be1b9006a8, 0190c1d452a91c38a3462abdd81752be1b9006a8unaffected
LinuxLinux4.19, 0, 5.4.279, 5.10.221, 5.15.162, 6.1.96, 6.6.36, 6.9.7, 6.10affected
Weakness

CWE details

No CWE listed

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