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CVE-2026-74692— net/smc: fix TOCTOU race between smc_listen_out() and listener close

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 5.1版本存在安全漏洞，该漏洞源于net/smc中smc_listen_out()与监听器关闭之间的TOCTOU竞争条件，可能导致远程对端在服务器调用close()时打开TCP连接，从而耗尽内核内存。

CVSS 7.5 · High EPSS 0.70% · P52

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< 53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa affected
fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< feb71634bb1abab3e8fb5cde874b27001cc1282e affected
fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< 01865e1ddb126b25ac9eba5cdd7ec49e11183a64 affected
fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< 00f89433777236ced4771211047fb5d4cd581cea affected
fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< 78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67 affected
fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< ff5bcd804b5bc5c64736b7d318c20e12ea9506b8 affected
fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9< 185a4caeecabc150106deda1da170b09f2ad803f affected
d1d004585b40c212b338fc8a40cbaaf230ea4703 affected
… +10 more rows
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I. Basic Information for CVE-2026-74692

Vulnerability Information
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Vulnerability Title
net/smc: fix TOCTOU race between smc_listen_out() and listener close
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/smc: fix TOCTOU race between smc_listen_out() and listener close smc_listen_out() reads lsmc->sk.sk_state without the listener lock, then acquires lock_sock_nested() only after the check passes. This opens a window where smc_close_active() can transition the listener to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept queue, and release the lock, all between the lockless read and the delayed lock acquisition: smc_listen_work (smc_hs_wq) smc_close_active() ------------------------------- ------------------------- release_sock(child) if (sk_state == SMC_LISTEN) TRUE lock_sock(listener) sk_state = SMC_CLOSED smc_close_cleanup_listen() release_sock(listener) flush_work(tcp_listen_work) lock_sock_nested(listener) smc_accept_enqueue(listener, child) /* child enqueued on dead listener */ smc_close_active() flushes only tcp_listen_work. Work items already dispatched onto smc_hs_wq for the CLC handshake continue running unguarded. smc_accept_enqueue() takes a sock_hold() on the child that is never released, so the child smc_sock, its clcsock, and the reference all leak. A remote peer that opens TCP connections while the server calls close() can exhaust kernel memory. Move lock_sock_nested() to before the sk_state check so that the test and the enqueue are atomic under the listener lock.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 5.1版本存在安全漏洞，该漏洞源于net/smc中smc_listen_out()与监听器关闭之间的TOCTOU竞争条件，可能导致远程对端在服务器调用close()时打开TCP连接，从而耗尽内核内存。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 ~ 53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa -
Linux Linux 5.1 -

II. Public POCs for CVE-2026-74692

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III. Intelligence Information for CVE-2026-74692

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Patches & Fixes for CVE-2026-74692 (6)

Same Patch Batch · Linux · 2026-08-22 · 149 CVEs total

CVE-2026-74705 10.0 CRITICAL udp: fix potential use-after-free in tunnel segmentation
CVE-2026-74612 10.0 CRITICAL veth: fix skb length accounting after XDP frag adjustment
CVE-2026-74669 9.8 CRITICAL ipvs: clear IPv4 options after rebasing tunnel ICMP errors
CVE-2026-74628 9.8 CRITICAL net/x25: fix use-after-free of the socket by its timers
CVE-2026-74723 9.8 CRITICAL btrfs: lzo: reject inline extents without valid headers
CVE-2026-74617 9.8 CRITICAL dibs: initialise dibs->lock in dibs_dev_alloc()
CVE-2026-74616 9.8 CRITICAL xdp: reject clones that overrun skb_shared_info tailroom
CVE-2026-74611 9.8 CRITICAL tls: rx: restore msg_iter before TLS 1.3 optimistic retry
CVE-2026-74608 9.8 CRITICAL smb: client: Fix use-after-free in cifs_try_adding_channels()
CVE-2026-74688 9.8 CRITICAL sctp: clear control chunk transport if it is being removed
CVE-2026-74727 9.8 CRITICAL ovpn: skip rehash for peers already removed from by_id
CVE-2026-74662 9.8 CRITICAL inet: frags: publish queues before arming timer
CVE-2026-74597 9.8 CRITICAL ip6_tunnel: clear skb2->cb[] in ip6ip6_err()
CVE-2026-74588 9.8 CRITICAL sctp: keep chunk->transport in step with the list it is queued on
CVE-2026-74730 9.8 CRITICAL NFS: Pin the 'struct nfs_server' during a FREE_STATEID call
CVE-2026-74586 9.8 CRITICAL sctp: clear new_transport when removing a peer
CVE-2026-74587 9.8 CRITICAL sctp: fix use-after-free of cached ASCONF chunk
CVE-2026-74591 9.8 CRITICAL mm/filemap: __filemap_add_folio() restore index before retrying
CVE-2026-74712 9.3 CRITICAL vdpa/mlx5: Fix buffer length in create_direct_keys()
CVE-2026-74665 9.1 CRITICAL net: fix skb length accounting after generic XDP frag adjustment

Showing top 20 of 149 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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