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CVE-2026-74483— binfmt_misc: don't leak the user namespace when the mount fails

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存在安全漏洞，该漏洞源于binfmt_misc在挂载失败时未正确释放用户命名空间引用，导致用户命名空间泄漏，攻击者可通过内存cgroup限制触发泄漏，造成拒绝服务。

AI Predicted 5.5 Difficulty: Easy EPSS 0.15% · P5

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 21ca59b365c091d583f36ac753eaa8baf947be6f< ffec017158d3aad8a6ffca1dfad63d63bde9caad affected
21ca59b365c091d583f36ac753eaa8baf947be6f< 867aed6a4848761190d5ebdedf9642648f97bceb affected
21ca59b365c091d583f36ac753eaa8baf947be6f< 87a4eb9bbb3497f749bbac612af22ddaa62d7b0d affected
21ca59b365c091d583f36ac753eaa8baf947be6f< b8206f516fe7cbe785cf44bf09c17c438d7c3cad affected
6.7 affected
< 6.7 unaffected
6.12.105≤ 6.12.* unaffected
6.18.46≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-74483

Vulnerability Information
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Vulnerability Title
binfmt_misc: don't leak the user namespace when the mount fails
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: binfmt_misc: don't leak the user namespace when the mount fails bm_get_tree() takes a reference to the user namespace and hands it to get_tree_keyed() as the sget key. sget_fc() moves that reference into sb->s_fs_info and clears fc->s_fs_info, so from that point on the superblock owns it and bm_free() doesn't see it anymore. The superblock drops it in ->put_super(). But generic_shutdown_super() only calls ->put_super() from inside the if (sb->s_root) branch, so nothing releases it when bm_fill_super() fails: - The kzalloc_obj() failure leaves s_root NULL and the whole branch is skipped. - A simple_fill_super() failure in the file loop leaves s_root set, but s_op still points at simple_super_operations, which has no ->put_super(). bm_fill_super() installs s_ops only once simple_fill_super() returned success, and installing it earlier wouldn't help either because simple_fill_super() overwrites s_op. Either way vfs_get_super() calls deactivate_locked_super() and the reference is gone for good. binfmt_misc mounts are available in a user namespace and both the inode and the dentry cache are SLAB_ACCOUNT, so an unprivileged caller under a tight memory cgroup can fail simple_fill_super() on demand and leak one user namespace per attempt. Drop the reference in ->kill_sb() instead, which runs unconditionally, the same way nfsd and rpc_pipefs release their keyed s_fs_info. That also stops ->put_super() from clearing s_fs_info while the superblock is still on @fs_supers. generic_shutdown_super() leaves it there on purpose so that sget_fc() keeps finding it until kill_sb() has run, but a NULL s_fs_info makes test_keyed_super() miss it, so a concurrent mount for the same user namespace skips the grab_super() wait and creates a second superblock for a namespace that is still being torn down.
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存在安全漏洞，该漏洞源于binfmt_misc在挂载失败时未正确释放用户命名空间引用，导致用户命名空间泄漏，攻击者可通过内存cgroup限制触发泄漏，造成拒绝服务。
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 21ca59b365c091d583f36ac753eaa8baf947be6f ~ ffec017158d3aad8a6ffca1dfad63d63bde9caad -
Linux Linux 6.7 -

II. Public POCs for CVE-2026-74483

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III. Intelligence Information for CVE-2026-74483

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Patches & Fixes for CVE-2026-74483 (4)

Same Patch Batch · Linux · 2026-08-15 · 845 CVEs total

CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72221 9.8 CRITICAL sunrpc: wait for in-flight TLS handshake callback when cancel loses race
CVE-2026-72466 9.8 CRITICAL xprtrdma: Fix bcall rep leak and unbounded peek
CVE-2026-72323 9.8 CRITICAL ipv4: igmp: Fix potential UAF in igmp_gq_start_timer()
CVE-2026-72463 9.8 CRITICAL xfrm: Fix dev use-after-free in xfrm async resumption
CVE-2026-72069 9.8 CRITICAL locking/rt: Fix the incorrect RCU protection in rt_spin_unlock()
CVE-2026-72339 9.8 CRITICAL qede: fix off-by-one in BD ring consumption on build_skb failure
CVE-2026-72065 9.8 CRITICAL net: mana: Validate the packet length reported by the NIC
CVE-2026-72064 9.8 CRITICAL net: mana: Sync page pool RX frags for CPU
CVE-2026-74255 9.8 CRITICAL tipc: fix UAF in tipc_l2_send_msg()
CVE-2026-74376 9.8 CRITICAL md/raid10: reset read_slot when reusing r10bio for discard
CVE-2026-72234 9.8 CRITICAL batman-adv: access unicast_ttvn skb->data only after skb realloc
CVE-2026-72041 9.8 CRITICAL espintcp: use sk_msg_free_partial to fix partial send

Showing top 20 of 845 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-74483

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