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CVE-2026-23233NVD status: Analyzed

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-23233 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions d4534a7f6c92baaf7e12a45fc6e37332cafafc33, 1ff415eef513bf12deb058fc50d57788c46c48e6, fee27b69dde1a05908b350eea42937af2387c4fe as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.18% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to d4534a7f6c92baaf7e12a45fc6e37332cafafc33 or 1ff415eef513bf12deb058fc50d57788c46c48e6 or fee27b69dde1a05908b350eea42937af2387c4fe or 607cb9d83838d2cd9f0406c2403ed61aadf0edff, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.127 or 6.12.74 or 6.18.13 or 6.19.3, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux40d76c393cca83938b11eb7ca8983aa3cd0ed69b up to, but not including, d4534a7f6c92baaf7e12a45fc6e37332cafafc33; 9703d69d9d153bb230711d0d577454552aeb13d4 up to, but not including, 1ff415eef513bf12deb058fc50d57788c46c48e6; 9703d69d9d153bb230711d0d577454552aeb13d4 up to, but not including, fee27b69dde1a05908b350eea42937af2387c4fe; 9703d69d9d153bb230711d0d577454552aeb13d4 up to, but not including, 607cb9d83838d2cd9f0406c2403ed61aadf0edff; 9703d69d9d153bb230711d0d577454552aeb13d4 up to, but not including, 5c145c03188bc9ba1c29e0bc4d527a5978fc47f9; 6.6.33 up to, but not including, 6.6.127; 6.9d4534a7f6c92baaf7e12a45fc6e37332cafafc33, 1ff415eef513bf12deb058fc50d57788c46c48e6, fee27b69dde1a05908b350eea42937af2387c4fe, 607cb9d83838d2cd9f0406c2403ed61aadf0edff, 5c145c03188bc9ba1c29e0bc4d527a5978fc47f9, 6.6.127
LinuxLinux Kernel6.6.33 up to, but not including, 6.6.127; 6.9 up to, but not including, 6.12.74; 6.13 up to, but not including, 6.18.13; 6.19 up to, but not including, 6.19.36.6.127, 6.12.74, 6.18.13, 6.19.3

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid mapping wrong physical block for swapfile Xiaolong Guo reported a f2fs bug in bugzilla [1] [1] https://bugzilla.kernel.org/show_bug.cgi?id=220951 Quoted: "When using stress-ng's swap stress test on F2FS filesystem with kernel 6.6+, the system experiences data corruption leading to either: 1 dm-verity corruption errors and device reboot 2 F2FS node corruption errors and boot hangs The issue occurs specifically when: 1 Using F2FS filesystem (ext4 is unaffected) 2 Swapfile size is less than F2FS section size (2MB) 3 Swapfile has fragmented physical layout (multiple non-contiguous extents) 4 Kernel version is 6.6+ (6.1 is unaffected) The root cause is in check_swap_activate() function in fs/f2fs/data.c. When the first extent of a small swapfile (< 2MB) is not aligned to section boundaries, the function incorrectly treats it as the last extent, failing to map subsequent extents. This results in incorrect swap_extent creation where only the first extent is mapped, causing subsequent swap writes to overwrite wrong physical locations (other files' data). Steps to Reproduce 1 Setup a device with F2FS-formatted userdata partition 2 Compile stress-ng from https://github.com/ColinIanKing/stress-ng 3 Run swap stress test: (Android devices) adb shell "cd /data/stressng; ./stress-ng-64 --metrics-brief --timeout 60 --swap 0" Log: 1 Ftrace shows in kernel 6.6, only first extent is mapped during second f2fs_map_blocks call in check_swap_activate(): stress-ng-swap-8990: f2fs_map_blocks: ino=11002, file offset=0, start blkaddr=0x43143, len=0x1 (Only 4KB mapped, not the full swapfile) 2 in kernel 6.1, both extents are correctly mapped: stress-ng-swap-5966: f2fs_map_blocks: ino=28011, file offset=0, start blkaddr=0x13cd4, len=0x1 stress-ng-swap-5966: f2fs_map_blocks: ino=28011, file offset=1, start blkaddr=0x60c84b, len=0xff The problematic code is in check_swap_activate(): if ((pblock - SM_I(sbi)->main_blkaddr) % blks_per_sec || nr_pblocks % blks_per_sec || !f2fs_valid_pinned_area(sbi, pblock)) { bool last_extent = false; not_aligned++; nr_pblocks = roundup(nr_pblocks, blks_per_sec); if (cur_lblock + nr_pblocks > sis->max) nr_pblocks -= blks_per_sec; /* this extent is last one */ if (!nr_pblocks) { nr_pblocks = last_lblock - cur_lblock; last_extent = true; } ret = f2fs_migrate_blocks(inode, cur_lblock, nr_pblocks); if (ret) { if (ret == -ENOENT) ret = -EINVAL; goto out; } if (!last_extent) goto retry; } When the first extent is unaligned and roundup(nr_pblocks, blks_per_sec) exceeds sis->max, we subtract blks_per_sec resulting in nr_pblocks = 0. The code then incorrectly assumes this is the last extent, sets nr_pblocks = last_lblock - cur_lblock (entire swapfile), and performs migration. After migration, it doesn't retry mapping, so subsequent extents are never processed. " In order to fix this issue, we need to lookup block mapping info after we migrate all blocks in the tail of swapfile.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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