# CVE-2025-40123: linux: In the Linux kernel, the following vulnerability has been resolved:  bpf: Enforce expected_attach_type for tailcall c...

CVE-2025-40123 is fixed in 62 products on 1 platform, first by ALAS2023-2025-1253, released October 27, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-40123
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 27, 2025

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bpftool amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | bpftool-debuginfo amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | bpftool6.12 amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | bpftool6.12-debuginfo amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | dtb-aarch64 opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-64kb opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-64kb sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-64kb sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-azure opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-azure sles 15.7 | 6.4.0-150700.20.24.1 | [SUSE-SU-2026:0281-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0281-1.md) | Jan 23, 2026 |
| Linux | kernel-azure sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-debuginfo amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-debuginfo-common-aarch64 amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-debuginfo-common-x86_64 amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-default opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-default sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-default sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-default-base opensuse-leap 16.0 | 6.12.0-160000.9.1.160000.2.6 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-default-base sles 15.7 | 6.4.0-150700.53.28.1.150700.17.19.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-default-base sles 16.0 | 6.12.0-160000.9.1.160000.2.6 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-devel amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-docs opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-docs sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-docs sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-headers amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-kvmsmall opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-kvmsmall sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-libbpf amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-libbpf-debuginfo amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-libbpf-devel amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-libbpf-static amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-livepatch-6.1.156-177.286 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-livepatch-6.12.53-69.119 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel-livepatch-SLE15-SP7-RT_Update_8 sles 15.7 | 1-150700.1.3.1 | [SUSE-SU-2026:0278-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0278-1.md) | Jan 23, 2026 |
| Linux | kernel-livepatch-SLE15-SP7_Update_8 sles 15.7 | 1-150700.15.3.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-modules-extra amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-modules-extra-common amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-obs-build opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-obs-build sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-obs-qa opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-obs-qa sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-rt opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-source opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-source sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-source sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-source-azure sles 15.7 | 6.4.0-150700.20.24.1 | [SUSE-SU-2026:0281-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0281-1.md) | Jan 23, 2026 |
| Linux | kernel-syms opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-syms sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-syms sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel-syms-azure sles 15.7 | 6.4.0-150700.20.24.1 | [SUSE-SU-2026:0281-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0281-1.md) | Jan 23, 2026 |
| Linux | kernel-tools amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-tools-debuginfo amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-tools-devel amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | kernel-zfcpdump opensuse-leap 16.0 | 6.12.0-160000.9.1 | [OPENSUSE-SU-2026:20145-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20145-1.md) | Feb 2, 2026 |
| Linux | kernel-zfcpdump sles 15.7 | 6.4.0-150700.53.28.1 | [SUSE-SU-2026:0315-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0315-1.md) | Jan 28, 2026 |
| Linux | kernel-zfcpdump sles 16.0 | 6.12.0-160000.9.1 | [SUSE-SU-2026:20220-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20220-1.md) | Feb 2, 2026 |
| Linux | kernel6.12 amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-debuginfo amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-debuginfo-common-aarch64 amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-debuginfo-common-x86_64 amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-devel amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-headers amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-libbpf amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-libbpf-debuginfo amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-libbpf-devel amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-libbpf-static amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-modules-extra amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-modules-extra-common amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-tools amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-tools-debuginfo amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | kernel6.12-tools-devel amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | linux Debian 12.15 (bookworm) | 6.1.158-1 | [DEBIAN-CVE-2025-40123](https://patchblox.com/security/data/fix/linux/debian-cve-2025-40123.md) | Nov 12, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.12.57-1 | [DEBIAN-CVE-2025-40123](https://patchblox.com/security/data/fix/linux/debian-cve-2025-40123.md) | Nov 12, 2025 |
| Linux | linux Debian 14 | 6.17.6-1 | [DEBIAN-CVE-2025-40123](https://patchblox.com/security/data/fix/linux/debian-cve-2025-40123.md) | Nov 12, 2025 |
| Linux | perf amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | perf-debuginfo amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | perf6.12 amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | perf6.12-debuginfo amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | python3-perf amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | python3-perf-debuginfo amzn 2023 | 1:6.1.156-177.286.amzn2023 | [ALAS2023-2025-1253](https://patchblox.com/security/data/fix/linux/alas2023-2025-1253.md) | Oct 27, 2025 |
| Linux | python3-perf6.12 amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |
| Linux | python3-perf6.12-debuginfo amzn 2023 | 1:6.12.53-69.119.amzn2023 | [ALAS2023-2025-1254](https://patchblox.com/security/data/fix/linux/alas2023-2025-1254.md) | Oct 27, 2025 |

---

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