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🛡️ CVE-2023-52523 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

bpf, sockmap: Reject sk_msg egress redirects to non-TCP sockets

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:

<TASK>

? 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.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

CVE-2023-52523 is recorded against 2 packages.

  • kernel (from 6.2.0 up to 6.5.7)
  • linux-kernel

Timeline and source

Published on 2 March 2024 and last revised on 12 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

Other advisories for this package

kernel has other advisories on record. If you are patching this one, these are worth checking on the same host:

CVE-2023-52523 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2024-03-02
Updated 2026-08-20
Modified 2026-08-12

Affected Packages

Software From version Fixed in
kernel 6.2.0 6.5.7
linux-kernel — —

Similar Threats

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