# CVE-2023-52523: linux: In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Reject sk_msg egress redirects to... CVE-2023-52523 is fixed in 21 products on 1 platform, first by ALAS2023-2023-422, released October 30, 2023. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2023-52523 - Priority: Routine - CVSS: 5.5 (medium) - EPSS: 0.0024 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Oct 30, 2023 ## Description In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Reject sk_msg egress redirects to non-TCP sockets With a SOCKMAP/SOCKHASH map and an sk_msg program user can steer messages sent from one TCP socket (s1) to actually egress from another TCP socket (s2): tcp_bpf_sendmsg(s1) // = sk_prot->sendmsg tcp_bpf_send_verdict(s1) // __SK_REDIRECT case tcp_bpf_sendmsg_redir(s2) tcp_bpf_push_locked(s2) tcp_bpf_push(s2) tcp_rate_check_app_limited(s2) // expects tcp_sock tcp_sendmsg_locked(s2) // ditto There is a hard-coded assumption in the call-chain, that the egress socket (s2) is a TCP socket. However in commit 122e6c79efe1 ("sock_map: Update sock type checks for UDP") we have enabled redirects to non-TCP sockets. This was done for the sake of BPF sk_skb programs. There was no indention to support sk_msg send-to-egress use case. As a result, attempts to send-to-egress through a non-TCP socket lead to a crash due to invalid downcast from sock to tcp_sock: BUG: kernel NULL pointer dereference, address: 000000000000002f ... Call Trace: ? show_regs+0x60/0x70 ? __die+0x1f/0x70 ? page_fault_oops+0x80/0x160 ? do_user_addr_fault+0x2d7/0x800 ? rcu_is_watching+0x11/0x50 ? exc_page_fault+0x70/0x1c0 ? asm_exc_page_fault+0x27/0x30 ? tcp_tso_segs+0x14/0xa0 tcp_write_xmit+0x67/0xce0 __tcp_push_pending_frames+0x32/0xf0 tcp_push+0x107/0x140 tcp_sendmsg_locked+0x99f/0xbb0 tcp_bpf_push+0x19d/0x3a0 tcp_bpf_sendmsg_redir+0x55/0xd0 tcp_bpf_send_verdict+0x407/0x550 tcp_bpf_sendmsg+0x1a1/0x390 inet_sendmsg+0x6a/0x70 sock_sendmsg+0x9d/0xc0 ? sockfd_lookup_light+0x12/0x80 __sys_sendto+0x10e/0x160 ? syscall_enter_from_user_mode+0x20/0x60 ? __this_cpu_preempt_check+0x13/0x20 ? lockdep_hardirqs_on+0x82/0x110 __x64_sys_sendto+0x1f/0x30 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Reject selecting a non-TCP sockets as redirect target from a BPF sk_msg program to prevent the crash. When attempted, user will receive an EACCES error from send/sendto/sendmsg() syscall. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | bpftool-debuginfo amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-debuginfo amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-debuginfo-common-aarch64 amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-debuginfo-common-x86_64 amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-devel amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-headers amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-libbpf amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-libbpf-devel amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-libbpf-static amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-livepatch-6.1.59-84.139 amzn 2023 | 1.0-0.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-modules-extra amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-tools amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-tools-debuginfo amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | kernel-tools-devel amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | linux Debian 12.15 (bookworm) | 6.1.64-1 | [DEBIAN-CVE-2023-52523](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52523.md) | Mar 2, 2024 | | Linux | linux Debian 13.5 (trixie) | 6.5.8-1 | [DEBIAN-CVE-2023-52523](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52523.md) | Mar 2, 2024 | | Linux | linux Debian 14 | 6.5.8-1 | [DEBIAN-CVE-2023-52523](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52523.md) | Mar 2, 2024 | | Linux | perf amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | perf-debuginfo amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | python3-perf amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | | Linux | python3-perf-debuginfo amzn 2023 | 6.1.59-84.139.amzn2023 | [ALAS2023-2023-422](https://patchblox.com/security/data/fix/linux/alas2023-2023-422.md) | Oct 30, 2023 | --- Data as of 2026-11-09T07:25:28Z UTC. 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