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Linux KernelOperating system · Linux

CVE-2024-53171

HIGH · 7.8 CVSS v3.1 Published 2024-12-27
Fix available
A fix is available. Upgrade to 5.4.287 / 5.10.231 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: ubifs: authentication: Fix use-after-free in ubifs_tnc_end_commit After an insertion in TNC, the tree might split and cause a node to change its `znode->parent`. A further deletion of other nodes in the tree (which also could free the nodes), the aforementioned node's `znode->cparent` could still point to a freed node. This `znode->cparent` may not be updated when getting nodes to commit in `ubifs_tnc_start_commit()`. This could then trigger a use-after-free when accessing the `znode->cparent` in `write_index()` in `ubifs_tnc_end_commit()`. This can be triggered by running rm -f /etc/test-file.bin dd if=/dev/urandom of=/etc/test-file.bin bs=1M count=60 conv=fsync in a loop, and with `CONFIG_UBIFS_FS_AUTHENTICATION`. KASAN then reports: BUG: KASAN: use-after-free in ubifs_tnc_end_commit+0xa5c/0x1950 Write of size 32 at addr ffffff800a3af86c by task ubifs_bgt0_20/153 Call trace: dump_backtrace+0x0/0x340 show_stack+0x18/0x24 dump_stack_lvl+0x9c/0xbc print_address_description.constprop.0+0x74/0x2b0 kasan_report+0x1d8/0x1f0 kasan_check_range+0xf8/0x1a0 memcpy+0x84/0xf4 ubifs_tnc_end_commit+0xa5c/0x1950 do_commit+0x4e0/0x1340 ubifs_bg_thread+0x234/0x2e0 kthread+0x36c/0x410 ret_from_fork+0x10/0x20 Allocated by task 401: kasan_save_stack+0x38/0x70 __kasan_kmalloc+0x8c/0xd0 __kmalloc+0x34c/0x5bc tnc_insert+0x140/0x16a4 ubifs_tnc_add+0x370/0x52c ubifs_jnl_write_data+0x5d8/0x870 do_writepage+0x36c/0x510 ubifs_writepage+0x190/0x4dc __writepage+0x58/0x154 write_cache_pages+0x394/0x830 do_writepages+0x1f0/0x5b0 filemap_fdatawrite_wbc+0x170/0x25c file_write_and_wait_range+0x140/0x190 ubifs_fsync+0xe8/0x290 vfs_fsync_range+0xc0/0x1e4 do_fsync+0x40/0x90 __arm64_sys_fsync+0x34/0x50 invoke_syscall.constprop.0+0xa8/0x260 do_el0_svc+0xc8/0x1f0 el0_svc+0x34/0x70 el0t_64_sync_handler+0x108/0x114 el0t_64_sync+0x1a4/0x1a8 Freed by task 403: kasan_save_stack+0x38/0x70 kasan_set_track+0x28/0x40 kasan_set_free_info+0x28/0x4c __kasan_slab_free+0xd4/0x13c kfree+0xc4/0x3a0 tnc_delete+0x3f4/0xe40 ubifs_tnc_remove_range+0x368/0x73c ubifs_tnc_remove_ino+0x29c/0x2e0 ubifs_jnl_delete_inode+0x150/0x260 ubifs_evict_inode+0x1d4/0x2e4 evict+0x1c8/0x450 iput+0x2a0/0x3c4 do_unlinkat+0x2cc/0x490 __arm64_sys_unlinkat+0x90/0x100 invoke_syscall.constprop.0+0xa8/0x260 do_el0_svc+0xc8/0x1f0 el0_svc+0x34/0x70 el0t_64_sync_handler+0x108/0x114 el0t_64_sync+0x1a4/0x1a8 The offending `memcpy()` in `ubifs_copy_hash()` has a use-after-free when a node becomes root in TNC but still has a `cparent` to an already freed node. More specifically, consider the following TNC: zroot / / zp1 / / zn Inserting a new node `zn_new` with a key smaller then `zn` will trigger a split in `tnc_insert()` if `zp1` is full: zroot / \ / \ zp1 zp2 / \ / \ zn_new zn `zn->parent` has now been moved to `zp2`, *but* `zn->cparent` still points to `zp1`. Now, consider a removal of all the nodes _except_ `zn`. Just when `tnc_delete()` is about to delete `zroot` and `zp2`: zroot \ \ zp2 \ \ zn `zroot` and `zp2` get freed and the tree collapses: zn `zn` now becomes the new `zroot`. `get_znodes_to_commit()` will now only find `zn`, the new `zroot`, and `write_index()` will check its `znode->cparent` that wrongly points to the already freed `zp1`. `ubifs_copy_hash()` thus gets wrongly called with `znode->cparent->zbranch[znode->iip].hash` that triggers the use-after-free! Fix this by explicitly setting `znode->cparent` to `NULL` in `get_znodes_to_commit()` for the root node. The search for the dirty nodes ---truncated---

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.20, < 5.4.287>= 5.5, < 5.10.231>= 5.11, < 5.15.174>= 5.16, < 6.1.120>= 6.2, < 6.6.64>= 6.7, < 6.11.11>= 6.12, < 6.12.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.4.287 / 5.10.231 / 5.15.174 or later
Fixed in 5.4.2875.10.2315.15.174
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux kernel >= 5.4.287, >= 5.10.231, >= 5.15.174, or >= 6.1.120 (depending on which branch you are on)

  1. Identify the currently running Linux kernel version using `uname -r`
  2. Based on the current version, upgrade to a fixed release that includes the patch:
  3. - If running 4.20 to 5.4.x: upgrade to kernel >= 5.4.287
  4. - If running 5.5 to 5.10.x: upgrade to kernel >= 5.10.231
  5. - If running 5.11 to 5.15.x: upgrade to kernel >= 5.15.174
  6. - If running 5.16 to 6.1.x: upgrade to kernel >= 6.1.120
  7. - If running 6.2+: the vulnerability may already be fixed in recent stable releases
  8. After upgrading the kernel, reboot the system to load the fixed version
Caveat Kernel upgrades may require reboot and could introduce compatibility issues with proprietary kernel modules or specific hardware drivers; ensure backup and test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

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Peer-ranked notes from engineers who’ve handled CVE-2024-53171 in production — separate from our analysis above.

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