Linux Kernel up to 6.1.155/6.6.111/6.12.52/6.17.2 bpf_prog_test_run_xdp null pointer dereference

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CTI Interest Score
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5.5$0-$5k0.00

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 6.1.155/6.6.111/6.12.52/6.17.2. The impacted element is the function bpf_prog_test_run_xdp. This manipulation causes null pointer dereference. The identification of this vulnerability is CVE-2025-40123. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.1.155/6.6.111/6.12.52/6.17.2. Affected by this vulnerability is the function bpf_prog_test_run_xdp. The manipulation with an unknown input leads to a null pointer dereference vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: bpf: Enforce expected_attach_type for tailcall compatibility Yinhao et al. recently reported: Our fuzzer tool discovered an uninitialized pointer issue in the bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem. This leads to a NULL pointer dereference when a BPF program attempts to deference the txq member of struct xdp_buff object. The test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the entry point for bpf_prog_test_run_xdp() and its expected_attach_type can neither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot of a tailcall map it owns. progB's expected_attach_type must be BPF_XDP_DEVMAP to pass xdp_is_valid_access() validation. The program returns struct xdp_md's egress_ifindex, and the latter is only allowed to be accessed under mentioned expected_attach_type. progB is then inserted into the tailcall which progA calls. The underlying issue goes beyond XDP though. Another example are programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well as sock_addr_func_proto() have different logic depending on the programs' expected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME should not be allowed doing a tailcall into a program which calls bpf_bind() out of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT. In short, specifying expected_attach_type allows to open up additional functionality or restrictions beyond what the basic bpf_prog_type enables. The use of tailcalls must not violate these constraints. Fix it by enforcing expected_attach_type in __bpf_prog_map_compatible(). Note that we only enforce this for tailcall maps, but not for BPF devmaps or cpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and cpu_map_bpf_prog_run*() which set up a new environment / context and therefore these situations are not prone to this issue.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2025-40123 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 276782 (Debian dla-4379 : linux-config-6.1 - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.156, 6.6.112, 6.12.53, 6.17.3 or 6.18-rc1 eliminates this vulnerability. Applying the patch a99de19128aec0913f3d529f529fbbff5edfaff8/08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a/c1ad19b5d8e23123503dcaf2d4342e1b90b923ad/4540aed51b12bc13364149bf95f6ecef013197c0 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 (276782) and CERT Bund (WID-SEC-2025-2579). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel
  • RESF Rocky Linux

Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.7
VulDB Meta Temp Score: 5.5

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

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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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: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 276782
Nessus Name: Debian dla-4379 : linux-config-6.1 - security update

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.156/6.6.112/6.12.53/6.17.3/6.18-rc1
Patch: a99de19128aec0913f3d529f529fbbff5edfaff8/08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a/c1ad19b5d8e23123503dcaf2d4342e1b90b923ad/4540aed51b12bc13364149bf95f6ecef013197c0

Timelineinfo

04/16/2025 CVE reserved
11/12/2025 +210 days Advisory disclosed
11/12/2025 +0 days VulDB entry created
02/08/2026 +88 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-40123 (🔒)
GCVE (CVE): GCVE-0-2025-40123
GCVE (VulDB): GCVE-100-332119
CERT Bund: WID-SEC-2025-2579 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 11/12/2025 13:25
Updated: 02/08/2026 01:03
Changes: 11/12/2025 13:25 (58), 11/13/2025 10:11 (7), 11/28/2025 21:00 (2), 12/18/2025 01:16 (1), 12/30/2025 13:54 (1), 02/08/2026 01:03 (1)
Complete: 🔍
Cache ID: 216::103

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