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CVE-2026-45920— ext4: fix dirtyclusters double decrement on fs shutdown

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ext4文件系统在文件系统关闭时，错误路径中dirtyclusters计数器被重复递减，导致计数为负值，触发警告。

AI Predicted 5.5 Difficulty: Moderate EPSS 0.15% · P4

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 0087d9fb3f29f59e8d42c8b058376d80e5adde4c< 523d5a4df3c649fa305c89efb552ec62a1ce9d3d affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< ca408af08544d96769c93a3d81a7f63f61129e95 affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< 55576fa14771d33994c29a9ae960e07bb3f56c20 affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< dbc4e10619ed87a50e637b96f2e574df36a7a769 affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< 61e372122b6d95aec940fdaea0a16f988f359897 affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< 3924aea2c33df3864929c1acd178bfc29d8f005f affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< 81982a11406c5da6c6e2b188028e7056e16b7128 affected
0087d9fb3f29f59e8d42c8b058376d80e5adde4c< 94a8cea54cd935c54fa2fba70354757c0fc245e3 affected
… +10 more rows
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I. Basic Information for CVE-2026-45920

Vulnerability Information
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Vulnerability Title
ext4: fix dirtyclusters double decrement on fs shutdown
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ext4: fix dirtyclusters double decrement on fs shutdown fstests test generic/388 occasionally reproduces a warning in ext4_put_super() associated with the dirty clusters count: WARNING: CPU: 7 PID: 76064 at fs/ext4/super.c:1324 ext4_put_super+0x48c/0x590 [ext4] Tracing the failure shows that the warning fires due to an s_dirtyclusters_counter value of -1. IOW, this appears to be a spurious decrement as opposed to some sort of leak. Further tracing of the dirty cluster count deltas and an LLM scan of the resulting output identified the cause as a double decrement in the error path between ext4_mb_mark_diskspace_used() and the caller ext4_mb_new_blocks(). First, note that generic/388 is a shutdown vs. fsstress test and so produces a random set of operations and shutdown injections. In the problematic case, the shutdown triggers an error return from the ext4_handle_dirty_metadata() call(s) made from ext4_mb_mark_context(). The changed value is non-zero at this point, so ext4_mb_mark_diskspace_used() does not exit after the error bubbles up from ext4_mb_mark_context(). Instead, the former decrements both cluster counters and returns the error up to ext4_mb_new_blocks(). The latter falls into the !ar->len out path which decrements the dirty clusters counter a second time, creating the inconsistency. To avoid this problem and simplify ownership of the cluster reservation in this codepath, lift the counter reduction to a single place in the caller. This makes it more clear that ext4_mb_new_blocks() is responsible for acquiring cluster reservation (via ext4_claim_free_clusters()) in the !delalloc case as well as releasing it, regardless of whether it ends up consumed or returned due to failure.
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ext4文件系统在文件系统关闭时，错误路径中dirtyclusters计数器被重复递减，导致计数为负值，触发警告。
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 0087d9fb3f29f59e8d42c8b058376d80e5adde4c ~ 523d5a4df3c649fa305c89efb552ec62a1ce9d3d -
Linux Linux 2.6.29 -

II. Public POCs for CVE-2026-45920

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III. Intelligence Information for CVE-2026-45920

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Patches & Fixes for CVE-2026-45920 (7)

Same Patch Batch · Linux · 2026-05-27 · 275 CVEs total

CVE-2026-46039 9.8 CRITICAL rxgk: Fix potential integer overflow in length check
CVE-2026-45898 9.8 CRITICAL RDMA/iwcm: Fix workqueue list corruption by removing work_list
CVE-2026-45988 9.8 CRITICAL rxrpc: Fix re-decryption of RESPONSE packets
CVE-2026-45972 9.8 CRITICAL smb: client: fix potential UAF and double free in smb2_open_file()
CVE-2026-46043 9.1 CRITICAL RDMA/rxe: Validate pad and ICRC before payload_size() in rxe_rcv
CVE-2026-45945 8.8 HIGH iommu/vt-d: Fix race condition during PASID entry replacement
CVE-2026-46056 8.8 HIGH Bluetooth: hci_event: fix potential UAF in SSP passkey handlers
CVE-2026-45843 8.2 HIGH slip: bound decode() reads against the compressed packet length
CVE-2025-71311 8.2 HIGH fs/ntfs3: Initialize new folios before use
CVE-2026-46037 8.2 HIGH ipv4: icmp: validate reply type before using icmp_pointers
CVE-2026-46099 8.1 HIGH net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels
CVE-2026-46010 8.1 HIGH rxrpc: Fix error handling in rxgk_extract_token()
CVE-2026-46076 7.9 HIGH KVM: nSVM: Raise #UD if unhandled VMMCALL isn't intercepted by L1
CVE-2026-45909 7.8 HIGH clk: mediatek: Drop __initconst from gates
CVE-2026-45862 7.8 HIGH iommu/vt-d: Flush cache for PASID table before using it
CVE-2026-45956 7.8 HIGH drm/exynos: vidi: use priv->vidi_dev for ctx lookup in vidi_connection_ioctl()
CVE-2026-45910 7.8 HIGH RDMA/rxe: Fix race condition in QP timer handlers
CVE-2026-45942 7.8 HIGH ext4: fix e4b bitmap inconsistency reports
CVE-2026-45894 7.8 HIGH iommu/vt-d: Clear Present bit before tearing down PASID entry
CVE-2026-45933 7.8 HIGH bpf: Preserve id of register in sync_linked_regs()

Showing top 20 of 275 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-45920

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