Linux: Use After Free
CVE-2026-68426 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 4e695742396be18d5291c310a3d7c450959d647a, 4927ab8a8acc8db4fad33e803d1d35e0b16cef83, b58731e0570bfd3989999fc2baf9ee4fecd5bec6 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 0.5% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 4e695742396be18d5291c310a3d7c450959d647a or 4927ab8a8acc8db4fad33e803d1d35e0b16cef83 or b58731e0570bfd3989999fc2baf9ee4fecd5bec6 or 33e1b0d25ca0d2818c635ff80e6aa0d295e08a98, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | f53c723902d1ac5f0b0a11d7c9dcbff748dde74e up to, but not including, 4e695742396be18d5291c310a3d7c450959d647a; f53c723902d1ac5f0b0a11d7c9dcbff748dde74e up to, but not including, 4927ab8a8acc8db4fad33e803d1d35e0b16cef83; f53c723902d1ac5f0b0a11d7c9dcbff748dde74e up to, but not including, b58731e0570bfd3989999fc2baf9ee4fecd5bec6; f53c723902d1ac5f0b0a11d7c9dcbff748dde74e up to, but not including, 33e1b0d25ca0d2818c635ff80e6aa0d295e08a98; f53c723902d1ac5f0b0a11d7c9dcbff748dde74e up to, but not including, bbca7cc3b2b4b10afbfee99b81d9ee78f5423046; f53c723902d1ac5f0b0a11d7c9dcbff748dde74e up to, but not including, 3f4c3919baf0944ad96580467c302bc6c7758b00; 4.16 | 4e695742396be18d5291c310a3d7c450959d647a, 4927ab8a8acc8db4fad33e803d1d35e0b16cef83, b58731e0570bfd3989999fc2baf9ee4fecd5bec6, 33e1b0d25ca0d2818c635ff80e6aa0d295e08a98, bbca7cc3b2b4b10afbfee99b81d9ee78f5423046, 3f4c3919baf0944ad96580467c302bc6c7758b00 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: xfrm: fix stale skb->prev after async crypto steals a GSO segment skb_gso_segment() leaves the segment list head with ->prev pointing at the last segment, an invariant validate_xmit_skb_list() relies on when it sets its tail pointer (tail = skb->prev). When validate_xmit_xfrm() walks a GSO list and some segments are stolen by async crypto (->xmit() returns -EINPROGRESS), those segments are unlinked from the list but the head ->prev is never updated. If the last segment is the one stolen, the returned head still has ->prev pointing at it, even though it is now owned by the crypto engine and may be freed. validate_xmit_skb_list() later does tail->next = skb, writing through that stale pointer -- a use-after-free. Repoint skb->prev at the last retained segment before returning.
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.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- git.kernel.org/stable/c/33e1b0d25ca0d2818c635ff80e6aa0d295e08a98
- git.kernel.org/stable/c/3f4c3919baf0944ad96580467c302bc6c7758b00
- git.kernel.org/stable/c/4927ab8a8acc8db4fad33e803d1d35e0b16cef83
- git.kernel.org/stable/c/4e695742396be18d5291c310a3d7c450959d647a
- git.kernel.org/stable/c/b58731e0570bfd3989999fc2baf9ee4fecd5bec6
- git.kernel.org/stable/c/bbca7cc3b2b4b10afbfee99b81d9ee78f5423046
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.5 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
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