Linux Kernel up to 6.15-rc4 net_sched use after free

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.7	$0-$5k	0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.15-rc4. This affects an unknown part of the component net_sched. This manipulation causes use after free. The identification of this vulnerability is CVE-2025-37890. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.15-rc4 and classified as critical. Affected by this vulnerability is an unknown functionality of the component net_sched. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case). This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2025-37890 since 04/16/2025. The exploitation appears to be easy. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 01/21/2026).

The vulnerability scanner Nessus provides a plugin with the ID 237223 (Debian dsa-5925 : affs-modules-6.1.0-33-4kc-malta-di - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.182, 6.1.138, 6.6.90, 6.12.28, 6.14.6 or 6.15-rc5 eliminates this vulnerability. Applying the patch e3e949a39a91d1f829a4890e7dfe9417ac72e4d0/8df7d37d626430035b413b97cee18396b3450bef/6082a87af4c52f58150d40dec1716011d871ac21/2e7093c7a8aba5d4f8809f271488e5babe75e202/ac39fd4a757584d78ed062d4f6fd913f83bd98b5/141d34391abbb315d68556b7c67ad97885407547 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 (237223) and CERT Bund (WID-SEC-2025-1098). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• SUSE Linux
• Oracle Linux
• RESF Rocky Linux
• Open Source Linux Kernel
• Red Hat Enterprise Linux
• Dell Secure Connect Gateway
• Debian Linux
• Google Cloud Platform
• Amazon Linux 2
• Ubuntu Linux

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.15.181
• 6.1.137
• 6.6.0
• 6.6.1
• 6.6.2
• 6.6.3
• 6.6.4
• 6.6.5
• 6.6.6
• 6.6.7
• 6.6.8
• 6.6.9
• 6.6.10
• 6.6.11
• 6.6.12
• 6.6.13
• 6.6.14
• 6.6.15
• 6.6.16
• 6.6.17
• 6.6.18
• 6.6.19
• 6.6.20
• 6.6.21
• 6.6.22
• 6.6.23
• 6.6.24
• 6.6.25
• 6.6.26
• 6.6.27
• 6.6.28
• 6.6.29
• 6.6.30
• 6.6.31
• 6.6.32
• 6.6.33
• 6.6.34
• 6.6.35
• 6.6.36
• 6.6.37
• 6.6.38
• 6.6.39
• 6.6.40
• 6.6.41
• 6.6.42
• 6.6.43
• 6.6.44
• 6.6.45
• 6.6.46
• 6.6.47
• 6.6.48
• 6.6.49
• 6.6.50
• 6.6.51
• 6.6.52
• 6.6.53
• 6.6.54
• 6.6.55
• 6.6.56
• 6.6.57
• 6.6.58
• 6.6.59
• 6.6.60
• 6.6.61
• 6.6.62
• 6.6.63
• 6.6.64
• 6.6.65
• 6.6.66
• 6.6.67
• 6.6.68
• 6.6.69
• 6.6.70
• 6.6.71
• 6.6.72
• 6.6.73
• 6.6.74
• 6.6.75
• 6.6.76
• 6.6.77
• 6.6.78
• 6.6.79
• 6.6.80
• 6.6.81
• 6.6.82
• 6.6.83
• 6.6.84
• 6.6.85
• 6.6.86
• 6.6.87
• 6.6.88
• 6.6.89
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.12.19
• 6.12.20
• 6.12.21
• 6.12.22
• 6.12.23
• 6.12.24
• 6.12.25
• 6.12.26
• 6.12.27
• 6.14.0
• 6.14.1
• 6.14.2
• 6.14.3
• 6.14.4
• 6.14.5
• 6.15-rc1
• 6.15-rc2
• 6.15-rc3
• 6.15-rc4

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.7

VulDB Base Score: 8.0
VulDB Temp Score: 7.6
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 237223
Nessus Name: Debian dsa-5925 : affs-modules-6.1.0-33-4kc-malta-di - security update

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Kernel 5.15.182/6.1.138/6.6.90/6.12.28/6.14.6/6.15-rc5
Patch: e3e949a39a91d1f829a4890e7dfe9417ac72e4d0/8df7d37d626430035b413b97cee18396b3450bef/6082a87af4c52f58150d40dec1716011d871ac21/2e7093c7a8aba5d4f8809f271488e5babe75e202/ac39fd4a757584d78ed062d4f6fd913f83bd98b5/141d34391abbb315d68556b7c67ad97885407547

Timelineinfo

04/16/2025 🔍
05/16/2025 +30 days 🔍
05/16/2025 +0 days 🔍
01/21/2026 +250 days 🔍

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-37890 (🔍)
GCVE (CVE): GCVE-0-2025-37890
GCVE (VulDB): GCVE-100-309289
CERT Bund: WID-SEC-2025-1098 - Linux Kernel: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Entryinfo

Created: 05/16/2025 15:36
Updated: 01/21/2026 12:52
Changes: 05/16/2025 15:36 (58), 05/25/2025 03:14 (2), 06/04/2025 16:53 (1), 07/20/2025 19:37 (7), 07/27/2025 07:43 (1), 08/10/2025 20:32 (1), 09/12/2025 06:06 (1), 11/17/2025 19:31 (11), 01/21/2026 12:52 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

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