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CVE-2026-52906— 9p: fix access mode flags being ORed instead of replaced

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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于访问模式标志被OR运算而非替换，可能导致根用户无法执行chown或其他特权操作。

CVSS 7.7 · High EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 6

VendorProduct Version RangeStatus
Linux Linux 1f3e4142c0eb178089ea0cbc97506a061470ad27< b8f037e87a083291190204b959cda417aaf01058 affected
1f3e4142c0eb178089ea0cbc97506a061470ad27< da2346a48a5a1fed86c3fe3d73c0b60e7b3027c9 affected
6.19 affected
< 6.19 unaffected
7.0.4≤ 7.0.* unaffected
7.1≤ * unaffected
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I. Basic Information for CVE-2026-52906

Vulnerability Information
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Vulnerability Title
9p: fix access mode flags being ORed instead of replaced
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: 9p: fix access mode flags being ORed instead of replaced Since commit 1f3e4142c0eb ("9p: convert to the new mount API"), v9fs_apply_options() applies parsed mount flags with |= onto flags already set by v9fs_session_init(). For 9P2000.L, session_init sets V9FS_ACCESS_CLIENT as the default, so when the user mounts with "access=user", both bits end up set. Access mode checks compare against exact values, so having both bits set matches neither mode. This causes v9fs_fid_lookup() to fall through to the default switch case, using INVALID_UID (nobody/65534) instead of current_fsuid() for all fid lookups. Root is then unable to chown or perform other privileged operations. Fix by clearing the access mask before applying the user's choice.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于访问模式标志被OR运算而非替换，可能导致根用户无法执行chown或其他特权操作。
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 1f3e4142c0eb178089ea0cbc97506a061470ad27 ~ b8f037e87a083291190204b959cda417aaf01058 -
Linux Linux 6.19 -

II. Public POCs for CVE-2026-52906

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III. Intelligence Information for CVE-2026-52906

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Patches & Fixes for CVE-2026-52906 (2)

Same Patch Batch · Linux · 2026-06-09 · 21 CVEs total

CVE-2026-46325 9.8 CRITICAL RDMA/rxe: Fix iova-to-va conversion for MR page sizes != PAGE_SIZE
CVE-2026-46316 9.3 CRITICAL KVM: arm64: vgic-its: Drop the translation cache reference only for the erased entry
CVE-2026-46317 8.8 HIGH KVM: arm64: Reassign nested_mmus array behind mmu_lock
CVE-2026-46326 8.4 HIGH iio: pressure: mprls0025pa: fix spi_transfer struct initialisation
CVE-2026-46332 8.0 HIGH greybus: gb-beagleplay: bound bootloader receive buffering
CVE-2026-52907 7.8 HIGH media: rockchip: rkcif: fix off by one bugs
CVE-2026-46330 7.8 HIGH Revert "net/smc: Introduce TCP ULP support"
CVE-2026-46327 7.8 HIGH dm: fix unlocked test for dm_suspended_md
CVE-2026-46324 7.8 HIGH netfilter: nf_tables: use list_del_rcu for netlink hooks
CVE-2026-46323 7.8 HIGH net: gro: don't merge zcopy skbs
CVE-2026-46319 7.8 HIGH net/sched: act_ct: Only release RCU read lock after ct_ft
CVE-2026-46320 7.4 HIGH tap: free page on error paths in tap_get_user_xdp()
CVE-2026-46328 7.3 HIGH apparmor: fix rlimit for posix cpu timers
CVE-2026-46322 7.1 HIGH tun: free page on build_skb failure in tun_xdp_one()
CVE-2026-46321 7.1 HIGH tun: free page on short-frame rejection in tun_xdp_one()
CVE-2026-46315 io_uring/waitid: clear waitid info before copying it to userspace
CVE-2026-46318 Revert "mm/hugetlbfs: update hugetlbfs to use mmap_prepare"
CVE-2026-46329 erofs: handle end of filesystem properly for file-backed mounts
CVE-2026-52904 drm/nouveau: fix nvkm_device leak on aperture removal failure
CVE-2026-52905 mm/damon/core: disallow non-power of two min_region_sz on damon_start()

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-52906

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