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CVE Record

CVE-2025-68815: net/sched: ets: Remove drr class from the active list if it changes to strict

In the Linux kernel, the following vulnerability has been resolved: net/sched: ets: Remove drr class from the active list if it changes to strict Whenever a user issues an ets qdisc change command, transforming a drr class into a strict one, the ets code isn't checking whether that class was in the active list and removing it. This means that, if a user changes a strict class (which was in the active list) back to a drr one, that class will be added twice to the active list [1]. Doing so with the following commands: tc qdisc add dev lo root handle 1: ets bands 2 strict 1 tc qdisc add dev lo parent 1:2 handle 20: \ tbf rate 8bit burst 100b latency 1s tc filter add dev lo parent 1: basic classid 1:2 ping -c1 -W0.01 -s 56 127.0.0.1 tc qdisc change dev lo root handle 1: ets bands 2 strict 2 tc qdisc change dev lo root handle 1: ets bands 2 strict 1 ping -c1 -W0.01 -s 56 127.0.0.1 Will trigger the following splat with list debug turned on: [ 59.279014][ T365] ------------[ cut here ]------------ [ 59.279452][ T365] list_add double add: new=ffff88801d60e350, prev=ffff88801d60e350, next=ffff88801d60e2c0. [ 59.280153][ T365] WARNING: CPU: 3 PID: 365 at lib/list_debug.c:35 __list_add_valid_or_report+0x17f/0x220 [ 59.280860][ T365] Modules linked in: [ 59.281165][ T365] CPU: 3 UID: 0 PID: 365 Comm: tc Not tainted 6.18.0-rc7-00105-g7e9f13163c13-dirty #239 PREEMPT(voluntary) [ 59.281977][ T365] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 59.282391][ T365] RIP: 0010:__list_add_valid_or_report+0x17f/0x220 [ 59.282842][ T365] Code: 89 c6 e8 d4 b7 0d ff 90 0f 0b 90 90 31 c0 e9 31 ff ff ff 90 48 c7 c7 e0 a0 22 9f 48 89 f2 48 89 c1 4c 89 c6 e8 b2 b7 0d ff 90 <0f> 0b 90 90 31 c0 e9 0f ff ff ff 48 89 f7 48 89 44 24 10 4c 89 44 ... [ 59.288812][ T365] Call Trace: [ 59.289056][ T365] <TASK> [ 59.289224][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.289546][ T365] ets_qdisc_change+0xd2b/0x1e80 [ 59.289891][ T365] ? __lock_acquire+0x7e7/0x1be0 [ 59.290223][ T365] ? __pfx_ets_qdisc_change+0x10/0x10 [ 59.290546][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.290898][ T365] ? __mutex_trylock_common+0xda/0x240 [ 59.291228][ T365] ? __pfx___mutex_trylock_common+0x10/0x10 [ 59.291655][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.291993][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.292313][ T365] ? trace_contention_end+0xc8/0x110 [ 59.292656][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.293022][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.293351][ T365] tc_modify_qdisc+0x63a/0x1cf0 Fix this by always checking and removing an ets class from the active list when changing it to strict. [1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/net/sched/sch_ets.c?id=ce052b9402e461a9aded599f5b47e76bc727f7de#n663

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux traffic-scheduling flaw can corrupt an internal kernel list when an ETS queue class is repeatedly changed between deficit-round-robin and strict modes. The supplied reproduction triggers a kernel warning. The CVSS assessment indicates potentially severe confidentiality, integrity, and availability impact, but the sources do not demonstrate those outcomes.

Executive priority

Patch promptly on affected systems where local users or workloads can administer traffic scheduling. This is not supported as a remote or actively exploited threat, so prioritize by qdisc reachability and shared-host risk rather than treating every Linux system as equally exposed.

Technical view

During an ETS qdisc change from DRR to strict, the class can remain on the active list. Changing it back to DRR then inserts the same class twice, causing an invalid double-add. The documented fix removes the class from the active list whenever it becomes strict. Multiple Linux stable commits are referenced.

Likely exposure

Exposure is limited to affected Linux kernels using ETS traffic scheduling where a local user or process can issue the required qdisc changes. The supplied affected-version data is ambiguous, so version strings alone are insufficient; verify whether the relevant stable fix is present in each deployed kernel build.

Exploitation context

CVSS 3.1 rates this 7.8 with local access, low complexity, low privileges, and no user interaction. The bundle reports no KEV listing and provides no evidence of active exploitation. Its reproduction establishes list corruption and a warning, but not a demonstrated privilege escalation or broader compromise.

Researcher notes

The demonstrated state transition is DRR to strict without unlinking, followed by strict to DRR and duplicate insertion. The affected-version representation includes unusual and potentially conflicting entries, including "0" and commit identifiers. Use fix-commit presence and vendor package guidance as authoritative validation signals. No CWE was supplied.

Mitigation direction

  • Install a vendor-supported kernel containing the applicable referenced stable fix.
  • Check distribution or appliance vendor guidance before selecting a fixed package.
  • Restrict untrusted access to traffic-control and qdisc administration until patched.
  • Prioritize multi-user systems where local processes can modify ETS configurations.

Validation and detection

  • Inventory kernel builds and identify systems using ETS qdiscs.
  • Confirm each build includes the applicable referenced Linux stable commit.
  • Review authorization for users and processes permitted to modify qdiscs.
  • Monitor kernel logs for ETS-related warnings or list double-add reports.
  • Test vendor-fixed kernels in staging without reproducing corruption on production systems.
Prepared
Confidence
medium
Sources
9

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-2025-68815 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
0ADP providers
8Source links

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-2025-68815Attack 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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf517335a61ff8037b18ba1b0a002c1f82926a934, cd9b50adc6bb9ad3f7d244590a389522215865c4, cd9b50adc6bb9ad3f7d244590a389522215865c4, cd9b50adc6bb9ad3f7d244590a389522215865c4, cd9b50adc6bb9ad3f7d244590a389522215865c4, cd9b50adc6bb9ad3f7d244590a389522215865c4, cd9b50adc6bb9ad3f7d244590a389522215865c4, d05330672afe2e142ba97e63bd7c1faef76781bb, 5.10.62, 5.13.14unaffected
LinuxLinux5.14, 0, 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64, 6.18.3, 6.19affected
Weakness

CWE details

No CWE listed

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