Linux: Use After Free
CVE-2026-63831 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists versions 3a2b378b3a9ca75d3518d879148d2ad25b5714a9, 7a831bcd0486788283ef35e396d4282ee01bb0d5, ff976ef7c39199ebff33c18034636595016db9f0 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 0.31% 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 3a2b378b3a9ca75d3518d879148d2ad25b5714a9 or 7a831bcd0486788283ef35e396d4282ee01bb0d5 or ff976ef7c39199ebff33c18034636595016db9f0 or e28e7fd34c449028325322a3f5127b92594b7396, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.260 or 5.15.211 or 6.1.177 or 6.6.144, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, 3a2b378b3a9ca75d3518d879148d2ad25b5714a9; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, 7a831bcd0486788283ef35e396d4282ee01bb0d5; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, ff976ef7c39199ebff33c18034636595016db9f0; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, e28e7fd34c449028325322a3f5127b92594b7396; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, 993fd674fe85d114e6a8d3963033d4fbbc2170a8; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, bd968bdd568beacfdf98ec537a87527e85f1d0cf; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, 86d531337ea1ba02d9f2bc830d07c683d9bfaade; 03556e4d0dbbbf4af9df76f4a3839c86f6afb015 up to, but not including, 84a04eb5b210643bd67aab81ff805d32f62aa865; and 1 more ranges | 3a2b378b3a9ca75d3518d879148d2ad25b5714a9, 7a831bcd0486788283ef35e396d4282ee01bb0d5, ff976ef7c39199ebff33c18034636595016db9f0, e28e7fd34c449028325322a3f5127b92594b7396, 993fd674fe85d114e6a8d3963033d4fbbc2170a8, bd968bdd568beacfdf98ec537a87527e85f1d0cf |
| Linux | Linux Kernel | 3.16 up to, but not including, 5.10.260; 5.11 up to, but not including, 5.15.211; 5.16 up to, but not including, 6.1.177; 6.2 up to, but not including, 6.6.144; 6.7 up to, but not including, 6.12.95; 6.13 up to, but not including, 6.18.38; 6.19 up to, but not including, 7.1.3 | 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38 |
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
- AdjacentThe attacker must be on the same local network segment.
- 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:A/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: mac802154: llsec: add skb_cow_data() before in-place crypto llsec_do_encrypt_unauth(), llsec_do_encrypt_auth(), llsec_do_decrypt_unauth(), and llsec_do_decrypt_auth() all perform in-place cryptographic transformations on skb data. They build a scatterlist with sg_init_one() pointing into the skb's linear data area and then pass the same scatterlist as both src and dst to the crypto API (e.g. crypto_skcipher_encrypt/decrypt, crypto_aead_encrypt/decrypt). On the RX path, __ieee802154_rx_handle_packet() clones the received skb before handing it to each subscriber via ieee802154_subif_frame(). The cloned skb shares the same underlying data buffer via reference counting. When llsec_do_decrypt() subsequently modifies this shared buffer in place, it corrupts data that other clones -- potentially belonging to other sockets or subsystems -- still reference. On the TX path, similar data sharing can occur when an skb's head has been cloned (skb_cloned() returns true). The fix is to call skb_cow_data() before performing any in-place crypto operation. skb_cow_data() ensures that the skb's data area is not shared: if the skb head is cloned or the data spans multiple fragments, it copies the data into a private buffer that can be safely modified in place. This is the same pattern used by: - ESP (net/ipv4/esp4.c, net/ipv6/esp6.c) - MACsec (drivers/net/macsec.c) - WireGuard (drivers/net/wireguard/receive.c) - TIPC (net/tipc/crypto.c) Without this guard, in-place crypto on shared skb data leads to: - Silent data corruption of other skb clones - Use-after-free when the crypto API scatterwalk writes through a page that has already been freed by another clone's kfree_skb() - Kernel crashes under concurrent 802.15.4 traffic with security enabled (KASAN/KMSAN reports slab-use-after-free) Found by 0sec (https://0sec.ai) using automated source analysis.
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
- git.kernel.org/stable/c/3a2b378b3a9ca75d3518d879148d2ad25b5714a9
- git.kernel.org/stable/c/7a831bcd0486788283ef35e396d4282ee01bb0d5
- git.kernel.org/stable/c/84a04eb5b210643bd67aab81ff805d32f62aa865
- git.kernel.org/stable/c/86d531337ea1ba02d9f2bc830d07c683d9bfaade
- git.kernel.org/stable/c/993fd674fe85d114e6a8d3963033d4fbbc2170a8
- git.kernel.org/stable/c/bd968bdd568beacfdf98ec537a87527e85f1d0cf
- git.kernel.org/stable/c/e28e7fd34c449028325322a3f5127b92594b7396
- git.kernel.org/stable/c/ff976ef7c39199ebff33c18034636595016db9f0
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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