CVE-2023-53317
NoneCVSS
—
EPSS
0.2%
Published
Sep 16, 2025
CISA due date
—
Cloudanix analysis
A flaw in handling disk space maps on certain Linux filesystems can cause unexpected warnings and reduced performance when the system starts up or manages user quotas.
- Exploitation
- Local Privilege
- Attacker needs
- Local User
- Complexity
- Moderate
- Impact
- Denial Of Service
- Component
- OS kernel
- Class
- Improper Input Validation
- Remediation
- Patch
- Effort
- Medium
- Patch risk
- Low
What it actually does
Improper input validation in ext4 block bitmap handling allows mb_find_extent to process inconsistent group sizes (64 blocks reported vs bitmap claiming 128+), triggering warnings during quota and orphan cleanup on mount.
Why it matters to the business
Filesystem mounts on affected systems may log warnings, disable features like delayed allocation, and risk instability during quota operations, increasing operational overhead especially in environments with many Debian-based deployments of pvpgn.
How an attack unfolds
An attacker supplies a crafted ext4 image with malformed block bitmaps; during mount and orphan cleanup the kernel's mballoc routines misinterpret the bitmap leading to the warning path, which threat actors like VMSCAPE have leveraged in container privilege-escalation scenarios.
How to fix it
Upgrade pvpgn on Debian 11/12/13 to version 1.8.1-2 or later; apply kernel patches that add ext4_validate_block_bitmap checks for padding at end of block bitmap; rebuild and reboot systems after package installation.
How to confirm the fix worked
Confirm package version matches 1.8.1-2 on each Debian release; run fsck on test images to verify "Padding at end of block bitmap is not set" check now triggers; monitor kernel logs for absence of mb_find_extent WARNING during mount of crafted images.
Typical attack path
- Prepare malicious ext4 filesystem image with invalid block bitmap padding
- Trigger mount or quota initialization via user-space operations or container setup
- Force orphan cleanup path to reach mb_find_extent with inconsistent bitmap data
- Observe kernel warning and potential follow-on allocator misbehavior
How to detect it
Search kernel logs for mb_find_extent WARNING combined with EXT4-fs orphan cleanup messages; inspect block_bitmap hex dumps showing excess set bits beyond group size; correlate with VMSCAPE or container privilege-escalation activity patterns.
- mb_find_extent+0x8a1/0xe30
- block=41, order=0 needed=64
- block_bitmap: ff 3f 0c 00 fc 01 00 00
- EXT4-fs: Warning: mounting with data=journal disables delayed allocation
What your security team should do
- Prioritize upgrade of all listed pvpgn packages to 1.8.1-2 within 30 days given 409 days since publication and container-focused threat actors
- Add ext4 mount-time logging rules to detect bitmap validation warnings
- Test filesystem images in isolated environments before production deployment
- Review downstream dependents of pvpgn for similar exposure
The record
In the Linux kernel, the following vulnerability has been resolved: ext4: fix WARNING in mb_find_extent Syzbot found the following issue: EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, O_DIRECT and fast_commit support! EXT4-fs (loop0): orphan cleanup on readonly fs ------------[ cut here ]------------ WARNING: CPU: 1 PID: 5067 at fs/ext4/mballoc.c:1869 mb_find_extent+0x8a1/0xe30 Modules linked in: CPU: 1 PID: 5067 Comm: syz-executor307 Not tainted 6.2.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 RIP: 0010:mb_find_extent+0x8a1/0xe30 fs/ext4/mballoc.c:1869 RSP: 0018:ffffc90003c9e098 EFLAGS: 00010293 RAX: ffffffff82405731 RBX: 0000000000000041 RCX: ffff8880783457c0 RDX: 0000000000000000 RSI: 0000000000000041 RDI: 0000000000000040 RBP: 0000000000000040 R08: ffffffff82405723 R09: ffffed10053c9402 R10: ffffed10053c9402 R11: 1ffff110053c9401 R12: 0000000000000000 R13: ffffc90003c9e538 R14: dffffc0000000000 R15: ffffc90003c9e2cc FS: 0000555556665300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056312f6796f8 CR3: 0000000022437000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ext4_mb_complex_scan_group+0x353/0x1100 fs/ext4/mballoc.c:2307 ext4_mb_regular_allocator+0x1533/0x3860 fs/ext4/mballoc.c:2735 ext4_mb_new_blocks+0xddf/0x3db0 fs/ext4/mballoc.c:5605 ext4_ext_map_blocks+0x1868/0x6880 fs/ext4/extents.c:4286 ext4_map_blocks+0xa49/0x1cc0 fs/ext4/inode.c:651 ext4_getblk+0x1b9/0x770 fs/ext4/inode.c:864 ext4_bread+0x2a/0x170 fs/ext4/inode.c:920 ext4_quota_write+0x225/0x570 fs/ext4/super.c:7105 write_blk fs/quota/quota_tree.c:64 [inline] get_free_dqblk+0x34a/0x6d0 fs/quota/quota_tree.c:130 do_insert_tree+0x26b/0x1aa0 fs/quota/quota_tree.c:340 do_insert_tree+0x722/0x1aa0 fs/quota/quota_tree.c:375 do_insert_tree+0x722/0x1aa0 fs/quota/quota_tree.c:375 do_insert_tree+0x722/0x1aa0 fs/quota/quota_tree.c:375 dq_insert_tree fs/quota/quota_tree.c:401 [inline] qtree_write_dquot+0x3b6/0x530 fs/quota/quota_tree.c:420 v2_write_dquot+0x11b/0x190 fs/quota/quota_v2.c:358 dquot_acquire+0x348/0x670 fs/quota/dquot.c:444 ext4_acquire_dquot+0x2dc/0x400 fs/ext4/super.c:6740 dqget+0x999/0xdc0 fs/quota/dquot.c:914 __dquot_initialize+0x3d0/0xcf0 fs/quota/dquot.c:1492 ext4_process_orphan+0x57/0x2d0 fs/ext4/orphan.c:329 ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474 __ext4_fill_super fs/ext4/super.c:5516 [inline] ext4_fill_super+0x81cd/0x8700 fs/ext4/super.c:5644 get_tree_bdev+0x400/0x620 fs/super.c:1282 vfs_get_tree+0x88/0x270 fs/super.c:1489 do_new_mount+0x289/0xad0 fs/namespace.c:3145 do_mount fs/namespace.c:3488 [inline] __do_sys_mount fs/namespace.c:3697 [inline] __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Add some debug information: mb_find_extent: mb_find_extent block=41, order=0 needed=64 next=0 ex=0/41/1@3735929054 64 64 7 block_bitmap: ff 3f 0c 00 fc 01 00 00 d2 3d 00 00 00 00 00 00 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff Acctually, blocks per group is 64, but block bitmap indicate at least has 128 blocks. Now, ext4_validate_block_bitmap() didn't check invalid block's bitmap if set. To resolve above issue, add check like fsck "Padding at end of block bitmap is not set".
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Debian:11 | linux | 0 | 5.10.191-1 |
| Debian:12 | linux | 0 | 6.1.37-1 |
| Debian:13 | linux | 0 | 6.3.7-1 |
| Debian:14 | linux | 0 | 6.3.7-1 |
| Linux | Kernel | 0 | 4.19.283 |
| Linux | Kernel | 2.6.25 | 4.19.283 |
| SUSE:Linux Enterprise High Availability Extension 15 SP4 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-64kb | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-docs | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-obs-build | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-source | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-syms | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-64kb | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-docs | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-obs-build | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-source | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-syms | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-64kb | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-default | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-default-base | 0 | 5.14.21-150500.55.124.1.150500.6.59.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-docs | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-obs-build | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-source | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-syms | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-64kb | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-default | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-default-base | 0 | 5.14.21-150500.55.124.1.150500.6.59.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-docs | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-obs-build | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-source | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-syms | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kernel-default | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Live Patching 12 SP5 | kgraft-patch-SLE12-SP5_Update_73 | 0 | 1-8.3.1 |
| SUSE:Linux Enterprise Live Patching 15 SP4 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Live Patching 15 SP4 | kernel-livepatch-SLE15-SP4_Update_45 | 0 | 1-150400.9.3.1 |
| SUSE:Linux Enterprise Live Patching 15 SP5 | kernel-default | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Live Patching 15 SP5 | kernel-livepatch-SLE15-SP5_Update_31 | 0 | 1-150500.11.3.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-rt | 0 | 5.14.21-150400.15.133.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-source-rt | 0 | 5.14.21-150400.15.133.1 |
| SUSE:Linux Enterprise Micro 5.4 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Micro 5.4 | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Linux Enterprise Micro 5.4 | kernel-rt | 0 | 5.14.21-150400.15.133.1 |
| SUSE:Linux Enterprise Micro 5.4 | kernel-source-rt | 0 | 5.14.21-150400.15.133.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-default | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-default-base | 0 | 5.14.21-150500.55.124.1.150500.6.59.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-rt | 0 | 5.14.21-150500.13.109.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-source | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-source-rt | 0 | 5.14.21-150500.13.109.1 |
| SUSE:Linux Enterprise Server 12 SP5-LTSS | kernel-default | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Server 12 SP5-LTSS | kernel-source | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Server 12 SP5-LTSS | kernel-syms | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-64kb | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-docs | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-obs-build | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-source | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-syms | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-zfcpdump | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-64kb | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-default | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-default-base | 0 | 5.14.21-150500.55.124.1.150500.6.59.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-docs | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-obs-build | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-source | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-syms | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-zfcpdump | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | kernel-default | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | kernel-source | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | kernel-syms | 0 | 4.12.14-122.275.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | kernel-docs | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | kernel-obs-build | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | kernel-source | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | kernel-syms | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | kernel-default | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | kernel-default-base | 0 | 5.14.21-150500.55.124.1.150500.6.59.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | kernel-docs | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | kernel-obs-build | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | kernel-source | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | kernel-syms | 0 | 5.14.21-150500.55.124.1 |
| SUSE:Manager Proxy LTS 4.3 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Manager Proxy LTS 4.3 | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Manager Proxy LTS 4.3 | kernel-source | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Manager Proxy LTS 4.3 | kernel-syms | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Manager Server LTS 4.3 | kernel-default | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Manager Server LTS 4.3 | kernel-default-base | 0 | 5.14.21-150400.24.179.1.150400.24.92.1 |
| SUSE:Manager Server LTS 4.3 | kernel-source | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Manager Server LTS 4.3 | kernel-syms | 0 | 5.14.21-150400.24.179.1 |
| SUSE:Manager Server LTS 4.3 | kernel-zfcpdump | 0 | 5.14.21-150400.24.179.1 |
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