Linux Kernel up to 6.1.146/6.6.99/6.12.39/6.15.7 htb_enqueue null pointer dereference

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Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.1.146/6.6.99/6.12.39/6.15.7. Impacted is the function htb_enqueue. Performing a manipulation results in null pointer dereference. This vulnerability was named CVE-2025-38468. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.1.146/6.6.99/6.12.39/6.15.7. This affects the function htb_enqueue. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree htb_lookup_leaf has a BUG_ON that can trigger with the following: tc qdisc del dev lo root tc qdisc add dev lo root handle 1: htb default 1 tc class add dev lo parent 1: classid 1:1 htb rate 64bit tc qdisc add dev lo parent 1:1 handle 2: netem tc qdisc add dev lo parent 2:1 handle 3: blackhole ping -I lo -c1 -W0.001 127.0.0.1 The root cause is the following: 1. htb_dequeue calls htb_dequeue_tree which calls the dequeue handler on the selected leaf qdisc 2. netem_dequeue calls enqueue on the child qdisc 3. blackhole_enqueue drops the packet and returns a value that is not just NET_XMIT_SUCCESS 4. Because of this, netem_dequeue calls qdisc_tree_reduce_backlog, and since qlen is now 0, it calls htb_qlen_notify -> htb_deactivate -> htb_deactiviate_prios -> htb_remove_class_from_row -> htb_safe_rb_erase 5. As this is the only class in the selected hprio rbtree, __rb_change_child in __rb_erase_augmented sets the rb_root pointer to NULL 6. Because blackhole_dequeue returns NULL, netem_dequeue returns NULL, which causes htb_dequeue_tree to call htb_lookup_leaf with the same hprio rbtree, and fail the BUG_ON The function graph for this scenario is shown here: 0) | htb_enqueue() { 0) + 13.635 us | netem_enqueue(); 0) 4.719 us | htb_activate_prios(); 0) # 2249.199 us | } 0) | htb_dequeue() { 0) 2.355 us | htb_lookup_leaf(); 0) | netem_dequeue() { 0) + 11.061 us | blackhole_enqueue(); 0) | qdisc_tree_reduce_backlog() { 0) | qdisc_lookup_rcu() { 0) 1.873 us | qdisc_match_from_root(); 0) 6.292 us | } 0) 1.894 us | htb_search(); 0) | htb_qlen_notify() { 0) 2.655 us | htb_deactivate_prios(); 0) 6.933 us | } 0) + 25.227 us | } 0) 1.983 us | blackhole_dequeue(); 0) + 86.553 us | } 0) # 2932.761 us | qdisc_warn_nonwc(); 0) | htb_lookup_leaf() { 0) | BUG_ON(); ------------------------------------------ The full original bug report can be seen here [1]. We can fix this just by returning NULL instead of the BUG_ON, as htb_dequeue_tree returns NULL when htb_lookup_leaf returns NULL. [1] https://lore.kernel.org/netdev/pF5XOOIim0IuEfhI-SOxTgRvNoDwuux7UHKnE_Y5-zVd4wmGvNk2ceHjKb8ORnzw0cGwfmVu42g9dL7XyJLf1NEzaztboTWcm0Ogxuojoeo=@willsroot.io/

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-38468 since 04/16/2025. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 265792 (SUSE SLES15 Security Update : kernel (SUSE-SU-2025:03310-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.147, 6.6.100, 6.12.40 or 6.15.8 eliminates this vulnerability. Applying the patch 890a5d423ef0a7bd13447ceaffad21189f557301/7ff2d83ecf2619060f30ecf9fad4f2a700fca344/e5c480dc62a3025b8428d4818e722da30ad6804f/3691f84269a23f7edd263e9b6edbc27b7ae332f4/0e1d5d9b5c5966e2e42e298670808590db5ed628 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 (265792) and CERT Bund (WID-SEC-2025-1665). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Google Container-Optimized OS
• 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
• NetApp ActiveIQ Unified Manager
• Dell PowerProtect Data Domain
• Open Source Linux Kernel
• Dell NetWorker
• Dell Secure Connect Gateway
• IBM Security Verify Access

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.1.146
• 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
• 6.6.90
• 6.6.91
• 6.6.92
• 6.6.93
• 6.6.94
• 6.6.95
• 6.6.96
• 6.6.97
• 6.6.98
• 6.6.99
• 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
• 6.12.28
• 6.12.29
• 6.12.30
• 6.12.31
• 6.12.32
• 6.12.33
• 6.12.34
• 6.12.35
• 6.12.36
• 6.12.37
• 6.12.38
• 6.12.39
• 6.15.0
• 6.15.1
• 6.15.2
• 6.15.3
• 6.15.4
• 6.15.5
• 6.15.6
• 6.15.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
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CPE 2.2info

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CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.6
VulDB Meta Temp Score: 5.5

VulDB Base Score: 5.7
VulDB Temp Score: 5.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

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

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Null pointer dereference
CWE: CWE-476 / CWE-404
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: 265792
Nessus Name: SUSE SLES15 Security Update : kernel (SUSE-SU-2025:03310-1)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.147/6.6.100/6.12.40/6.15.8
Patch: 890a5d423ef0a7bd13447ceaffad21189f557301/7ff2d83ecf2619060f30ecf9fad4f2a700fca344/e5c480dc62a3025b8428d4818e722da30ad6804f/3691f84269a23f7edd263e9b6edbc27b7ae332f4/0e1d5d9b5c5966e2e42e298670808590db5ed628

Timelineinfo

04/16/2025 CVE reserved
07/28/2025 +103 days Advisory disclosed
07/28/2025 +0 days VulDB entry created
01/25/2026 +181 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-38468 (🔒)
GCVE (CVE): GCVE-0-2025-38468
GCVE (VulDB): GCVE-100-317883
CERT Bund: WID-SEC-2025-1665 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 07/28/2025 14:44
Updated: 01/25/2026 13:46
Changes: 07/28/2025 14:44 (58), 08/17/2025 19:38 (7), 08/18/2025 08:26 (1), 08/18/2025 12:05 (1), 08/20/2025 12:17 (1), 08/26/2025 14:45 (1), 08/29/2025 00:12 (1), 09/25/2025 03:47 (2), 09/30/2025 11:43 (1), 10/18/2025 07:35 (1), 11/02/2025 00:36 (1), 11/16/2025 19:16 (1), 12/22/2025 21:09 (10), 01/21/2026 09:46 (1), 01/25/2026 13:46 (1)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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