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CVE-2026-99040— KEYS: Fix add_key() race with keyring restriction

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： KEYS：修复 add_key() 与密钥环限制之间的竞态条件在获取目标密钥环的信号量（semaphore）之前，便对进行了快照读取。而在安装限制时，是持有该信号量的。这种时序差异导致写入者可能观察到“无限制”的状态，随后等待密钥环所有者安装“拒绝所有”的限制并返回成功，接着利用之前读取的过时 NULL 快照将密钥链接到密钥环中。该写入者仅需对目标密钥环拥有写入权限即可触发此问题。修复方法是将的读取操作移至和之后执行。这样，读取操作及随后的限制检查便能通

AI Predicted 7.8 Difficulty: Moderate EPSS 0.18% · P8 Updated Oct 23, 2026

Possible ATT&CK Techniques 1 AI

T1548.001 · Setuid and Setgid

Affected Version Matrix 12

Vendor	Product	Version Range	Status
Linux	Linux	`5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c< 305f1828b871dd46bf41addeb6f11d2c162dcb25`	affected
		`5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c< f99399b48e3edd6851fac34cd329bab9f1f33baf`	affected
		`5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c< 11516a0c402a6c1fa52254aa70d8d65fb921e59e`	affected
		`5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c< da0b595d8e6e2dd798f6e34e09dc51a13b888514`	affected
		`5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c< dd3ea3fcba7c75493760cdbccd35f029597e8d5e`	affected
		`4.7`	affected
		`< 4.7`	unaffected
		`6.6.160≤ 6.6.*`	unaffected
… +4 more rows

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Vulnerability Information

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Vulnerability Title

KEYS: Fix add_key() race with keyring restriction

Source: CVE Program / CVE List V5

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: KEYS: Fix add_key() race with keyring restriction __key_create_or_update() snapshots keyring->restrict_link before taking the destination keyring's semaphore. keyring_restrict() installs a restriction while holding that semaphore. This allows a writer to observe no restriction, wait for the keyring owner to install a reject-all restriction and return successfully, and then link a key using the stale NULL snapshot. The writer only needs write permission on the destination keyring. Move the restrict_link read after __key_link_lock() and __key_link_begin(). The read and the subsequent restriction check are then serialized with restriction installation by keyring->sem. The race was reproduced on v7.2.8 in 19 executions where restriction installation returned before the link completed. All 19 linked the key despite the reject-all restriction. With this change, 312 executions reached the same ordering and every add_key() call failed with -EPERM. The issue was found by manual concurrency analysis assisted by AI-based analysis and independently verified with a QEMU reproducer and kernel instrumentation.

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	5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c ~ 305f1828b871dd46bf41addeb6f11d2c162dcb25	-
Linux	Linux	4.7	-

II. Public POCs for CVE-2026-99040

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-99040

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Patches & Fixes for CVE-2026-99040 (5)

https://www.cve.org/CVERecord?id=CVE-2026-99040

Same Patch Batch · Linux · 2026-10-23 · 217 CVEs total

CVE-2026-98959	9.8 CRITICAL	btrfs: fix xattr replace when multiple xattrs are packed in the same item
CVE-2026-99078	9.8 CRITICAL	net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry
CVE-2026-99079	9.8 CRITICAL	net/mlx5e: Prevent stale XSK buffer release on refill retry
CVE-2026-98988	8.8 HIGH	namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE
CVE-2026-99083	8.8 HIGH	ksmbd: fix heap out-of-bounds write in krb5_authenticate()
CVE-2026-99082	8.8 HIGH	KVM: x86: Use active memslots for the per-vCPU MMIO cache
CVE-2026-98981	8.8 HIGH	namespace: unhash a dentry before detaching the mounts on it
CVE-2026-98980	8.8 HIGH	namei: don't reveal overmounted entries in refwalk
CVE-2026-98870	8.8 HIGH	ksmbd: remove stale channels from all sessions on teardown
CVE-2026-98978	8.4 HIGH	namespace: never expire a locked mount
CVE-2026-99042	8.4 HIGH	io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6
CVE-2026-98968	8.1 HIGH	amt: send the relay's General Query directly from the receive path
CVE-2026-99064	8.1 HIGH	cipso: adjust cached option offsets when removing CIPSO
CVE-2026-99014	7.8 HIGH	Bluetooth: hci_sync: Fix command skb lifetime during scan setup
CVE-2026-98999	7.8 HIGH	drm/xe: Fix stale pinned_link entry when fb-pin performs the final unpin
CVE-2026-99016	7.8 HIGH	riscv: futex: untag the user pointer before the atomic access
CVE-2026-99018	7.8 HIGH	riscv: entry: gate shadow call stack reload on sstatus.SPP, not tp
CVE-2026-99051	7.8 HIGH	fsverity: RCU-delay the freeing of struct fsverity_info
CVE-2026-99054	7.8 HIGH	tipc: destroy topsrv workqueues before closing connections
CVE-2026-99053	7.8 HIGH	tipc: hold a reference to nodes found by link name

Showing top 20 of 217 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

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Same vendor: Linux