CVE-2026-99133— net/iucv: fix the recvmsg window update

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.

在 Linux 内核中，以下漏洞已得到修复： net/iucv：修复 recvmsg 窗口更新问题函数在未检查传输层类型的情况下，发送了仅适用于 HiperSockets 的标志。因此，在经典的 z/VM 套接字上，会通过一个为 NULL 的指针来设置套接字缓冲区（skb）的大小。由于接受值为 1，导致结果为 0，此时只需对自身的套接字执行一次调用，未授权进程即可触发虚假断开连接。此外，该函数在持有自旋锁的情况下调用，而在该被视作原子操作的代码段中执行了级别的内存分配。若将发送操作移至锁外，则

AI Predicted 5.5 Difficulty: Moderate Updated Oct 28, 2026

Possible ATT&CK Techniques 2 AI

T1190 · Exploit Public-Facing Application T1068 · Exploitation for Privilege Escalation

Updated Oct 28, 2026

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Vulnerability Information

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Vulnerability Title

net/iucv: fix the recvmsg window update

Source: CVE Program / CVE List V5

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net/iucv: fix the recvmsg window update iucv_sock_recvmsg() sends the HiperSockets-only AF_IUCV_FLAG_WIN without testing the transport, so on a classic z/VM socket iucv_send_ctrl() sizes the skb through a NULL iucv->hs_dev. SO_MSGLIMIT accepts 1, so msglimit / 2 is zero and one recvmsg() on its own socket is enough for an unprivileged process to take a spurious disconnect. It also calls iucv_send_ctrl() under spin_lock_bh(&message_q.lock), which allocates GFP_KERNEL inside a section the code treats as atomic. Sending outside that lock lets two recvmsg() reach afiucv_hs_send() at once, where msg_recv is sampled for the advertised window and subtracted after dev_queue_xmit() -- and sendmsg reaches that counter under lock_sock() while recvmsg holds no socket lock, so both can subtract the same value, the counter goes negative and the credit reaches the peer twice. Test the transport, claim the credit with atomic_xchg() after the last error exit and hand it back if the transmit fails, and send once the lock is dropped.

Source: CVE Program / CVE List V5

CVSS Information

N/A

Source: CVE Program / CVE List V5

Vulnerability Type

N/A

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
Linux	Linux	3881ac441f642d56503818123446f7298442236b ~ 8f2efa742f4cfe7dd756154f8bc07350dbe3ec92	-
Linux	Linux	3.2	-

II. Public POCs for CVE-2026-99133

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III. Intelligence Information for CVE-2026-99133

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Patches & Fixes for CVE-2026-99133 (3)

https://www.cve.org/CVERecord?id=CVE-2026-99133

Same Patch Batch · Linux · 2026-10-28 · 117 CVEs total

CVE-2026-99144		sched_ext: Fix use-after-free of a destroyed user DSQ by a deferred reenqueue
CVE-2026-99129		selinux: fix BPF token permission checks
CVE-2026-99130		io_uring/cancel: don't spin on local work the task can't run
CVE-2026-99131		xfs: fix capability check in xfs
CVE-2026-99132		xfs: don't hold buffer locks across sync transaction commit in xfs_sync_sb_buf
CVE-2026-99134		mac802154: fix data race and NULL deref on local->assoc_dev
CVE-2026-99135		dm-integrity: fix infinite loop on discard with large tag size
CVE-2026-99137		cifs: don't update i_size in cifs_do_truncate without a cached handle
CVE-2026-99136		dm-crypt: fix a tiny race condition in crypt_dec_pending
CVE-2026-99138		tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)
CVE-2026-99140		tracing: Fix hist trigger timestamps for buffered events
CVE-2026-99139		tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)
CVE-2026-99141		tracing: Fix crash in print_graph_function_event()
CVE-2026-99142		tracing: Check operator stack capacity before pushing
CVE-2026-99143		tracing: Keep the predicate limit separate from program capacity
CVE-2026-99156		scsi: st: Fix use-after-free race between st_remove() and st_open()
CVE-2026-99153		scsi: libiscsi: Validate the ITT reflected in a Reject PDU
CVE-2026-99152		scsi: libiscsi: Validate the task named by a management response
CVE-2026-99154		scsi: libiscsi: Reject a negative task index from parse_pdu_itt
CVE-2026-99151		drm/amd/display: Fix NULL sink dereference in USB4 bandwidth functions

Showing top 20 of 117 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Linux

Same vendor: Linux