Linux: Use After Free
CVE-2025-21883 is a high-severity use after free 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 3c01102bec9592928e6b155da41cfcd5d25a2066, a4880583f88deba63504ce1c8287a70d39c01378, 34393fd78d7183a007eaf0090966ebedcc29bd57 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 0.22% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 3c01102bec9592928e6b155da41cfcd5d25a2066 or a4880583f88deba63504ce1c8287a70d39c01378 or 34393fd78d7183a007eaf0090966ebedcc29bd57 or 79990cf5e7aded76d0c092c9f5ed31eb1c75e02c, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.81 or 6.12.18 or 6.13.6, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 8cd8a6b17d275a45e3722d0215f6115b687c8c3e up to, but not including, 3c01102bec9592928e6b155da41cfcd5d25a2066; 8cd8a6b17d275a45e3722d0215f6115b687c8c3e up to, but not including, a4880583f88deba63504ce1c8287a70d39c01378; 8cd8a6b17d275a45e3722d0215f6115b687c8c3e up to, but not including, 34393fd78d7183a007eaf0090966ebedcc29bd57; 8cd8a6b17d275a45e3722d0215f6115b687c8c3e up to, but not including, 79990cf5e7aded76d0c092c9f5ed31eb1c75e02c; 6.4 | 3c01102bec9592928e6b155da41cfcd5d25a2066, a4880583f88deba63504ce1c8287a70d39c01378, 34393fd78d7183a007eaf0090966ebedcc29bd57, 79990cf5e7aded76d0c092c9f5ed31eb1c75e02c |
| Linux | Linux Kernel | 6.4 up to, but not including, 6.6.81; 6.7 up to, but not including, 6.12.18; 6.13 up to, but not including, 6.13.6; 6.14 | 6.6.81, 6.12.18, 6.13.6 |
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: ice: Fix deinitializing VF in error path If ice_ena_vfs() fails after calling ice_create_vf_entries(), it frees all VFs without removing them from snapshot PF-VF mailbox list, leading to list corruption. Reproducer: devlink dev eswitch set $PF1_PCI mode switchdev ip l s $PF1 up ip l s $PF1 promisc on sleep 1 echo 1 > /sys/class/net/$PF1/device/sriov_numvfs sleep 1 echo 1 > /sys/class/net/$PF1/device/sriov_numvfs Trace (minimized): list_add corruption. next->prev should be prev (ffff8882e241c6f0), but was 0000000000000000. (next=ffff888455da1330). kernel BUG at lib/list_debug.c:29! RIP: 0010:__list_add_valid_or_report+0xa6/0x100 ice_mbx_init_vf_info+0xa7/0x180 [ice] ice_initialize_vf_entry+0x1fa/0x250 [ice] ice_sriov_configure+0x8d7/0x1520 [ice] ? __percpu_ref_switch_mode+0x1b1/0x5d0 ? __pfx_ice_sriov_configure+0x10/0x10 [ice] Sometimes a KASAN report can be seen instead with a similar stack trace: BUG: KASAN: use-after-free in __list_add_valid_or_report+0xf1/0x100 VFs are added to this list in ice_mbx_init_vf_info(), but only removed in ice_free_vfs(). Move the removing to ice_free_vf_entries(), which is also being called in other places where VFs are being removed (including ice_free_vfs() itself).
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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