Linux: Use After Free
CVE-2026-63970 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 72194f65050958e4c8e069adb6c5d89ef81ca197, b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d, 5d317573f1d48e76cce5fb6250452b6e4102e0fb 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.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 72194f65050958e4c8e069adb6c5d89ef81ca197 or b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d or 5d317573f1d48e76cce5fb6250452b6e4102e0fb or 1e584c304cfb94a759417130b1fc6d30b30c4cce, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.97 or 6.18.35 or 7.0.12, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 581512a6dc939ef122e49336626ae159f3b8a345 up to, but not including, 72194f65050958e4c8e069adb6c5d89ef81ca197; 581512a6dc939ef122e49336626ae159f3b8a345 up to, but not including, b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d; 581512a6dc939ef122e49336626ae159f3b8a345 up to, but not including, 5d317573f1d48e76cce5fb6250452b6e4102e0fb; 581512a6dc939ef122e49336626ae159f3b8a345 up to, but not including, 1e584c304cfb94a759417130b1fc6d30b30c4cce; 6.7 | 72194f65050958e4c8e069adb6c5d89ef81ca197, b62e2b2b4a50953ca952f3cd3f77dd62dc50fd5d, 5d317573f1d48e76cce5fb6250452b6e4102e0fb, 1e584c304cfb94a759417130b1fc6d30b30c4cce |
| Linux | Linux Kernel | 6.7 up to, but not including, 6.12.97; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.1 | 6.12.97, 6.18.35, 7.0.12 |
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 CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: bind uarg before filling zerocopy skb virtio_transport_send_pkt_info() allocates or reuses the zerocopy uarg before entering the send loop, but virtio_transport_alloc_skb() still fills the skb before it inherits that uarg. When fixed-buffer vectored zerocopy hits MAX_SKB_FRAGS, io_sg_from_iter() may partially attach managed frags and return -EMSGSIZE. The rollback path call kfree_skb() to free an skb that carries SKBFL_MANAGED_FRAG_REFS but no uarg, so skb_release_data() falls through to ordinary frag unref. Pass the uarg into virtio_transport_alloc_skb() and bind it immediately before virtio_transport_fill_skb(). This keeps control or no-payload skbs untouched while ensuring success and rollback share one lifetime rule.
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: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 9.8 Critical severity
- 8.8 High severity
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