CVE-2026-74307: Linux kernel · ext4: validate donor file superblock early in EXT4_IOC_MOVE_EXT
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in fb52013cad9e9b7d3a6a14ea1bcd841e41da7c6c : update Linux kernel when convenient.
Data as of 26 Oct 2026, 13:47 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in fb52013cad9e9b7d3a6a14ea1bcd841e41da7c6c, c143957520c6c9b5cd72e0de8b52b814f0c576fe, 74796e886ca39fcb0d3fd36ea6a39c62784ab6fb +2
Exploitation evidence
Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in– |
Description
In the Linux kernel, the following vulnerability has been resolved: ext4: validate donor file superblock early in EXT4_IOC_MOVE_EXT Reject the EXT4_IOC_MOVE_EXT ioctl early if the donor file does not belong to the same superblock as the original file. Currently, this validation is performed inside ext4_move_extents() by mext_check_validity(), but only after lock_two_nondirectories() has already acquired the inode locks. When the donor fd refers to a file on a different filesystem (e.g., overlayfs), this late validation creates a circular lock dependency: CPU0 (overlayfs write) CPU1 (ext4 ioctl) ---- ---- inode_lock(ovl_inode) mnt_want_write_file(filp) sb_start_write(ext4_sb) [sb_writers] backing_file_write_iter() vfs_iter_write(real_file) file_start_write(real_file) sb_start_write(ext4_sb) [blocked by freeze] lock_two_nondirectories() inode_lock(ovl_inode) [blocked] With a concurrent freeze operation holding sb_writers write side, this forms a deadlock cycle: CPU0 waits for freeze to complete, freeze waits for CPU1's sb_writers reader to exit, CPU1 waits for CPU0's inode lock. Since EXT4_IOC_MOVE_EXT exchanges physical extents between two files, it fundamentally requires both files to reside on the same ext4 filesystem. Moving the superblock check before any lock acquisition is both semantically correct and eliminates the circular dependency by ensuring that cross-filesystem donor fds are rejected before sb_writers or inode locks are taken.
References
- git.kernel.org/stable/c/663f184b51492093d408e518efc95ee13b5b4440 (opens in a new tab)
- git.kernel.org/stable/c/74796e886ca39fcb0d3fd36ea6a39c62784ab6fb (opens in a new tab)
- git.kernel.org/stable/c/29e07ec352f0ad06c833a18bf47d82c81f55544f (opens in a new tab)
- git.kernel.org/stable/c/fb52013cad9e9b7d3a6a14ea1bcd841e41da7c6c (opens in a new tab)
- git.kernel.org/stable/c/c143957520c6c9b5cd72e0de8b52b814f0c576fe (opens in a new tab)