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CVE-2026-89595— fsnotify: Fix stale object mask after concurrent mark updates

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 2.6.31版本存在安全漏洞，该漏洞源于fsnotify在并发标记更新时因缓存聚合已包含事件位而跳过对象掩码重新计算，存在竞争条件，可能导致对象掩码过期，造成fanotify无法产生FAN_MODIFY事件或inotify丢失IN_MODIFY事件。

AI Predicted 5.5 Difficulty: Hard EPSS 0.22% · P11

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 63c882a05416e18de6fb59f7dd6da48f3bbe8273< 27d172b60eeca5c8fd51b246f9fb959067cf102b affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< 2f09f08d602647fc4e328fc27ecb4c3008d10338 affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< de75382d6e354b2b055df4896d12a91969f12090 affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< 343ae18e960f6c5f1d34d58a69750c62cd463228 affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< 92289e66639f62abc754c6f3bce5ead7e98e4ee2 affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< 947400af98b9e63841929d079a2c3ea0a8ba227b affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< ac8d8b599d466a129122bded77db3d0f8b96b461 affected
63c882a05416e18de6fb59f7dd6da48f3bbe8273< e422777fdd4746de1109575c51e65038d4c5c1be affected
… +10 more rows
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I. Basic Information for CVE-2026-89595

Vulnerability Information
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Vulnerability Title
fsnotify: Fix stale object mask after concurrent mark updates
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: fsnotify: Fix stale object mask after concurrent mark updates When a mark gets a new event bit, fanotify and inotify may avoid recalculating the object mask if the cached aggregate already contains that bit. This is racy with a recalculation triggered by a concurrent update to another mark on the same connector. The concurrent scan can read the mark before the new bit is added, while the updater reads the old aggregate before that scan publishes its result. The updater then skips recalculation and the scan publishes a mask without the bit, leaving the object mask stale after both updates complete. This can be reproduced with two fanotify groups watching the same inode: one thread removes FAN_MODIFY from one existing mark while another thread adds FAN_MODIFY to the other mark. After both fanotify_mark() calls return, writes can fail to produce FAN_MODIFY for the group whose mark now contains the bit. This was reproduced on an unmodified v6.12.95 kernel. The equivalent inotify interleaving loses IN_MODIFY events. For normal fanotify additions, recalculate whenever the raw mark mask changes. The normal mask is not cleared asynchronously, so an unchanged addition cannot introduce missing interest. Always recalculate ignore-mask updates because FS_MODIFY handling may clear the ignore mask without taking mark->lock, making snapshot comparisons unreliable. Always recalculate after updating an existing inotify watch. Its replace path temporarily sets mark->mask to zero, so a concurrent scan can observe zero even when the old and final masks are equal. Assigning the replacement mask directly would avoid the transient zero, but existing-watch updates are infrequent, so unconditional recalculation is simpler.
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
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 2.6.31版本存在安全漏洞，该漏洞源于fsnotify在并发标记更新时因缓存聚合已包含事件位而跳过对象掩码重新计算，存在竞争条件，可能导致对象掩码过期，造成fanotify无法产生FAN_MODIFY事件或inotify丢失IN_MODIFY事件。
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 63c882a05416e18de6fb59f7dd6da48f3bbe8273 ~ 27d172b60eeca5c8fd51b246f9fb959067cf102b -
Linux Linux 2.6.31 -

II. Public POCs for CVE-2026-89595

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III. Intelligence Information for CVE-2026-89595

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Patches & Fixes for CVE-2026-89595 (8)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89656 9.8 CRITICAL libceph: reject buckets with mismatched CRUSH ids
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-89595

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