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CVE-2025-40237— fs/notify: call exportfs_encode_fid with s_umount

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exportfs_encode_fid未在s_umount保护下调用，可能导致空指针解引用。

AI Predicted 5.5 Difficulty: Hard EPSS 0.20% · P9

Affected Version Matrix 15

VendorProduct Version RangeStatus
Linux Linux a1a541fbfa7e97c1100144db34b57553d7164ce5< 950b604384fd75d62e860bec7135b2b62eb4d508 affected
f0c0ac84de17c37e6e84da65fb920f91dada55ad< bc1c6b803e14ea2b8f7e33b7164013f666ceb656 affected
3c7c90274ae339e1ad443c9be1c67a20b80b9c76< 3f307a9f7a7a2822e38ac451b73e2244e7279496 affected
c45beebfde34aa71afbc48b2c54cdda623515037< d1894bc542becb0fda61e7e513b09523cab44030 affected
c45beebfde34aa71afbc48b2c54cdda623515037< a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a affected
6.6.72< 6.6.73 affected
6.6.74< 6.6.115 affected
6.12.10< 6.12.56 affected
… +7 more rows
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I. Basic Information for CVE-2025-40237

Vulnerability Information
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Vulnerability Title
fs/notify: call exportfs_encode_fid with s_umount
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: fs/notify: call exportfs_encode_fid with s_umount Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr. This issue was found by syzkaller. Race Condition Diagram: Thread 1 Thread 2 -------- -------- generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL | | vfs_read() | inotify_fdinfo() | * inode get from mark * | show_mark_fhandle(m, inode) | exportfs_encode_fid(inode, ..) | ovl_encode_fh(inode, ..) | ovl_check_encode_origin(inode) | * deref i_sb->s_root * | | v fsnotify_sb_delete(sb) Which then leads to: [ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none) <snip registers, unreliable trace> [ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240 IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path. Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock. This form of fix was suggested by Amir in [1]. [1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/
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exportfs_encode_fid未在s_umount保护下调用，可能导致空指针解引用。
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 a1a541fbfa7e97c1100144db34b57553d7164ce5 ~ 950b604384fd75d62e860bec7135b2b62eb4d508 -
Linux Linux 6.13 -

II. Public POCs for CVE-2025-40237

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III. Intelligence Information for CVE-2025-40237

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Same Patch Batch · Linux · 2025-12-04 · 53 CVEs total

CVE-2025-40261 9.8 CRITICAL nvme: nvme-fc: Ensure ->ioerr_work is cancelled in nvme_fc_delete_ctrl()
CVE-2025-40252 9.8 CRITICAL net: qlogic/qede: fix potential out-of-bounds read in qede_tpa_cont() and qede_tpa_end()
CVE-2025-40258 9.8 CRITICAL mptcp: fix race condition in mptcp_schedule_work()
CVE-2025-40257 9.8 CRITICAL mptcp: fix a race in mptcp_pm_del_add_timer()
CVE-2025-40253 8.8 HIGH s390/ctcm: Fix double-kfree
CVE-2025-40266 8.2 HIGH KVM: arm64: Check the untrusted offset in FF-A memory share
CVE-2025-40244 7.8 HIGH hfsplus: fix KMSAN uninit-value issue in __hfsplus_ext_cache_extent()
CVE-2025-40251 7.8 HIGH devlink: rate: Unset parent pointer in devl_rate_nodes_destroy
CVE-2025-40262 7.8 HIGH Input: imx_sc_key - fix memory corruption on unload
CVE-2025-40250 7.8 HIGH net/mlx5: Clean up only new IRQ glue on request_irq() failure
CVE-2025-40248 7.8 HIGH vsock: Ignore signal/timeout on connect() if already established
CVE-2025-40249 7.8 HIGH gpio: cdev: make sure the cdev fd is still active before emitting events
CVE-2025-40245 7.8 HIGH nios2: ensure that memblock.current_limit is set when setting pfn limits
CVE-2025-40214 7.8 HIGH af_unix: Initialise scc_index in unix_add_edge().
CVE-2025-40243 7.8 HIGH hfs: fix KMSAN uninit-value issue in hfs_find_set_zero_bits()
CVE-2025-40241 7.8 HIGH erofs: fix crafted invalid cases for encoded extents
CVE-2025-40233 7.8 HIGH ocfs2: clear extent cache after moving/defragmenting extents
CVE-2025-40216 7.8 HIGH io_uring/rsrc: don't rely on user vaddr alignment
CVE-2025-40215 7.8 HIGH xfrm: delete x->tunnel as we delete x
CVE-2025-40240 7.5 HIGH sctp: avoid NULL dereference when chunk data buffer is missing

Showing top 20 of 53 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-40237

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