Linux Kernel up to 6.16-rc5 qdisc_tree_reduce_backlog privilege escalation

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5.4$0-$5k0.00

Summaryinfo

A vulnerability categorized as problematic has been discovered in Linux Kernel up to 6.16-rc5. This vulnerability affects the function qdisc_tree_reduce_backlog. Such manipulation leads to an unknown weakness. This vulnerability is listed as CVE-2025-38457. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 6.16-rc5. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: net/sched: Abort __tc_modify_qdisc if parent class does not exist Lion's patch [1] revealed an ancient bug in the qdisc API. Whenever a user creates/modifies a qdisc specifying as a parent another qdisc, the qdisc API will, during grafting, detect that the user is not trying to attach to a class and reject. However grafting is performed after qdisc_create (and thus the qdiscs' init callback) is executed. In qdiscs that eventually call qdisc_tree_reduce_backlog during init or change (such as fq, hhf, choke, etc), an issue arises. For example, executing the following commands: sudo tc qdisc add dev lo root handle a: htb default 2 sudo tc qdisc add dev lo parent a: handle beef fq Qdiscs such as fq, hhf, choke, etc unconditionally invoke qdisc_tree_reduce_backlog() in their control path init() or change() which then causes a failure to find the child class; however, that does not stop the unconditional invocation of the assumed child qdisc's qlen_notify with a null class. All these qdiscs make the assumption that class is non-null. The solution is ensure that qdisc_leaf() which looks up the parent class, and is invoked prior to qdisc_create(), should return failure on not finding the class. In this patch, we leverage qdisc_leaf to return ERR_PTRs whenever the parentid doesn't correspond to a class, so that we can detect it earlier on and abort before qdisc_create is called. [1] https://lore.kernel.org/netdev/[email protected]/

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2025-38457 since 04/16/2025. Technical details are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 253428 (SUSE SLES15 Security Update : kernel (SUSE-SU-2025:02923-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.296, 5.10.240, 5.15.189, 6.1.146, 6.6.99, 6.12.39, 6.15.7 or 6.16-rc6 eliminates this vulnerability. Applying the patch 923a276c74e25073ae391e930792ac86a9f77f1e/90436e72c9622c2f70389070088325a3232d339f/25452638f133ac19d75af3f928327d8016952c8e/23c165dde88eac405eebb59051ea1fe139a45803/4c691d1b6b6dbd73f30ed9ee7da05f037b0c49af/8ecd651ef24ab50123692a4e3e25db93cb11602a/e28a383d6485c3bb51dc5953552f76c4dea33eea/ffdde7bf5a439aaa1955ebd581f5c64ab1533963 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (253428), EUVD (EUVD-2025-22684) and CERT Bund (WID-SEC-2025-1653). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • IBM QRadar SIEM
  • SUSE openSUSE
  • RESF Rocky Linux
  • Dell Avamar
  • Open Source Linux Kernel
  • Dell NetWorker
  • Dell Secure Connect Gateway

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 253428
Nessus Name: SUSE SLES15 Security Update : kernel (SUSE-SU-2025:02923-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.4.296/5.10.240/5.15.189/6.1.146/6.6.99/6.12.39/6.15.7/6.16-rc6
Patch: 923a276c74e25073ae391e930792ac86a9f77f1e/90436e72c9622c2f70389070088325a3232d339f/25452638f133ac19d75af3f928327d8016952c8e/23c165dde88eac405eebb59051ea1fe139a45803/4c691d1b6b6dbd73f30ed9ee7da05f037b0c49af/8ecd651ef24ab50123692a4e3e25db93cb11602a/e28a383d6485c3bb51dc5953552f76c4dea33eea/ffdde7bf5a439aaa1955ebd581f5c64ab1533963

Timelineinfo

04/16/2025 CVE reserved
07/25/2025 +100 days Advisory disclosed
07/25/2025 +0 days VulDB entry created
01/03/2026 +162 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-38457 (🔒)
GCVE (CVE): GCVE-0-2025-38457
GCVE (VulDB): GCVE-100-317738
EUVD: 🔒
CERT Bund: WID-SEC-2025-1653 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 07/25/2025 19:31
Updated: 01/03/2026 23:51
Changes: 07/25/2025 19:31 (56), 07/30/2025 03:38 (1), 08/22/2025 03:54 (2), 08/22/2025 22:33 (7), 09/15/2025 05:37 (1), 09/29/2025 02:26 (1), 11/02/2025 13:58 (1), 12/23/2025 00:48 (10), 12/23/2025 08:51 (1), 01/03/2026 23:51 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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