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CVE Record

CVE-2024-36938: bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue

In the Linux kernel, the following vulnerability has been resolved: bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue Fix NULL pointer data-races in sk_psock_skb_ingress_enqueue() which syzbot reported [1]. [1] BUG: KCSAN: data-race in sk_psock_drop / sk_psock_skb_ingress_enqueue write to 0xffff88814b3278b8 of 8 bytes by task 10724 on cpu 1: sk_psock_stop_verdict net/core/skmsg.c:1257 [inline] sk_psock_drop+0x13e/0x1f0 net/core/skmsg.c:843 sk_psock_put include/linux/skmsg.h:459 [inline] sock_map_close+0x1a7/0x260 net/core/sock_map.c:1648 unix_release+0x4b/0x80 net/unix/af_unix.c:1048 __sock_release net/socket.c:659 [inline] sock_close+0x68/0x150 net/socket.c:1421 __fput+0x2c1/0x660 fs/file_table.c:422 __fput_sync+0x44/0x60 fs/file_table.c:507 __do_sys_close fs/open.c:1556 [inline] __se_sys_close+0x101/0x1b0 fs/open.c:1541 __x64_sys_close+0x1f/0x30 fs/open.c:1541 do_syscall_64+0xd3/0x1d0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 read to 0xffff88814b3278b8 of 8 bytes by task 10713 on cpu 0: sk_psock_data_ready include/linux/skmsg.h:464 [inline] sk_psock_skb_ingress_enqueue+0x32d/0x390 net/core/skmsg.c:555 sk_psock_skb_ingress_self+0x185/0x1e0 net/core/skmsg.c:606 sk_psock_verdict_apply net/core/skmsg.c:1008 [inline] sk_psock_verdict_recv+0x3e4/0x4a0 net/core/skmsg.c:1202 unix_read_skb net/unix/af_unix.c:2546 [inline] unix_stream_read_skb+0x9e/0xf0 net/unix/af_unix.c:2682 sk_psock_verdict_data_ready+0x77/0x220 net/core/skmsg.c:1223 unix_stream_sendmsg+0x527/0x860 net/unix/af_unix.c:2339 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x140/0x180 net/socket.c:745 ____sys_sendmsg+0x312/0x410 net/socket.c:2584 ___sys_sendmsg net/socket.c:2638 [inline] __sys_sendmsg+0x1e9/0x280 net/socket.c:2667 __do_sys_sendmsg net/socket.c:2676 [inline] __se_sys_sendmsg net/socket.c:2674 [inline] __x64_sys_sendmsg+0x46/0x50 net/socket.c:2674 do_syscall_64+0xd3/0x1d0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 value changed: 0xffffffff83d7feb0 -> 0x0000000000000000 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 10713 Comm: syz-executor.4 Tainted: G W 6.8.0-syzkaller-08951-gfe46a7dd189e #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024 Prior to this, commit 4cd12c6065df ("bpf, sockmap: Fix NULL pointer dereference in sk_psock_verdict_data_ready()") fixed one NULL pointer similarly due to no protection of saved_data_ready. Here is another different caller causing the same issue because of the same reason. So we should protect it with sk_callback_lock read lock because the writer side in the sk_psock_drop() uses "write_lock_bh(&sk->sk_callback_lock);". To avoid errors that could happen in future, I move those two pairs of lock into the sk_psock_data_ready(), which is suggested by John Fastabend.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2024-36938 is a Linux kernel bug in BPF sockmap/skmsg handling. A race can leave a callback pointer NULL while another path uses it, causing a NULL pointer dereference. The provided sources show a kernel fix, but no CVSS score, severity, or active exploitation evidence.

Executive priority

Treat as a kernel maintenance item until vendor advisories clarify severity. No active exploitation is shown in the provided sources, but kernel crashes on shared infrastructure can affect availability, so include it in normal patch cycles.

Technical view

The issue is a data race in sk_psock_skb_ingress_enqueue() involving saved_data_ready during sk_psock_drop(). The fix protects sk_psock_data_ready() with sk_callback_lock, matching the writer-side locking. syzbot/KCSAN reported the race on a 6.8 syzkaller kernel.

Likely exposure

Exposure is limited to Linux systems running affected kernel builds with BPF sockmap/skmsg functionality reachable. The bundle lists Linux kernel version records including 4.20, 5.10.223, 5.15.159, 6.1.91, 6.6.31, 6.8.10, and 6.9. Exact distribution package impact requires vendor mapping.

Exploitation context

The bundle contains a syzbot/KCSAN concurrency report and kernel stable fixes. It does not cite public exploitation, CISA KEV inclusion, exploit availability, privilege requirements, or impact beyond NULL pointer dereference behavior.

Researcher notes

The source evidence supports a race-condition NULL pointer dereference in net/core/skmsg.c fixed by locking around sk_psock_data_ready(). The record lacks CVSS, CWE, exploitability analysis, and distribution-specific affected package ranges, so validation should focus on kernel commit/package mapping.

Mitigation direction

  • Check Linux distribution advisories for CVE-2024-36938 package status.
  • Update kernels to vendor builds containing the referenced stable fixes.
  • Prioritize internet-facing or multi-tenant Linux hosts after vendor impact confirmation.
  • Track kernel versions separately for containers and host nodes.
  • Avoid inventing workarounds; follow vendor guidance if patching is delayed.

Validation and detection

  • Inventory running kernel versions across servers, appliances, and cloud images.
  • Map each kernel package to vendor advisory status for CVE-2024-36938.
  • Confirm fixed kernel builds are booted, not merely installed.
  • Review kernel logs for unusual NULL dereference crashes around skmsg or sockmap.
  • Document any unsupported kernels requiring upgrade or replacement.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2024-36938 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux604326b41a6fb9b4a78b6179335decee0365cd8c, 604326b41a6fb9b4a78b6179335decee0365cd8c, 604326b41a6fb9b4a78b6179335decee0365cd8c, 604326b41a6fb9b4a78b6179335decee0365cd8c, 604326b41a6fb9b4a78b6179335decee0365cd8c, 604326b41a6fb9b4a78b6179335decee0365cd8cunaffected
LinuxLinux4.20, 0, 5.10.223, 5.15.159, 6.1.91, 6.6.31, 6.8.10, 6.9affected
Weakness

CWE details

No CWE listed

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