Linux: Use After Free
CVE-2026-63801 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 remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 171d31245d11bf84836fad3b394cb465a4d008ec, 2d1f21419ec121232c916d3a3fc9b6766473a0e7, 0a780653b2a7569a7af9be7d0b00b1251baca63a 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 0.51% 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 171d31245d11bf84836fad3b394cb465a4d008ec or 2d1f21419ec121232c916d3a3fc9b6766473a0e7 or 0a780653b2a7569a7af9be7d0b00b1251baca63a or eaca7dae02fab70c8d223cffe03cec1b93249ce2, 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 | fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, 171d31245d11bf84836fad3b394cb465a4d008ec; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, 2d1f21419ec121232c916d3a3fc9b6766473a0e7; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, 0a780653b2a7569a7af9be7d0b00b1251baca63a; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, eaca7dae02fab70c8d223cffe03cec1b93249ce2; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, dca7713fe044a2067387948557ea099056e1679e; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, e18769616fd5a90ec1e12aabbba544c488284292; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, 1eea5e1820a2f5164d706bd1277bc97ff31ce32d; fc1b6d6de2208774efd2a20bf0daddb02d18b1e0 up to, but not including, bda3348872a2ef0d19f2df6aa8cb5025adce2f20; and 1 more ranges | 171d31245d11bf84836fad3b394cb465a4d008ec, 2d1f21419ec121232c916d3a3fc9b6766473a0e7, 0a780653b2a7569a7af9be7d0b00b1251baca63a, eaca7dae02fab70c8d223cffe03cec1b93249ce2, dca7713fe044a2067387948557ea099056e1679e, e18769616fd5a90ec1e12aabbba544c488284292 |
| Linux | Linux Kernel | 5.5 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
- NetworkCan be exploited remotely over a network, including the internet.
- 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:N/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: tipc: fix slab-use-after-free Read in tipc_aead_decrypt_done tipc_aead_decrypt() goes straight from tipc_bearer_hold(b) to crypto_aead_decrypt(req) without taking a reference on the netns, unlike the encrypt path. When crypto_aead_decrypt() is offloaded asynchronously (e.g. the SIMD aead wrapper queuing to cryptd), the cryptd worker runs tipc_aead_decrypt_done() later. If the bearer's netns is torn down in the meantime, cleanup_net() -> tipc_exit_net() -> tipc_crypto_stop() frees the per-netns tipc_crypto, and the completion then reads it: tipc_aead_decrypt_done() dereferences aead->crypto->stats and aead->crypto->net, and tipc_crypto_rcv_complete() dereferences aead->crypto->aead[] and the node table -- reading freed memory. Decoded KASAN splat (v7.1-rc7, CONFIG_KASAN_INLINE + TIPC + TIPC_CRYPTO): BUG: KASAN: slab-use-after-free in tipc_aead_decrypt_done (net/tipc/crypto.c:999) Read of size 8 at addr ffff8881056258a8 by task kworker/u16:2/51 Workqueue: events_unbound Call Trace: tipc_aead_decrypt_done (net/tipc/crypto.c:999) process_one_work (kernel/workqueue.c:3314) worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245) Allocated by task 169: __kasan_kmalloc (mm/kasan/common.c:398 mm/kasan/common.c:415) tipc_crypto_start (net/tipc/crypto.c:1502) tipc_init_net (net/tipc/core.c:72) ops_init (net/core/net_namespace.c:137) setup_net (net/core/net_namespace.c:446) copy_net_ns (net/core/net_namespace.c:579) create_new_namespaces (kernel/nsproxy.c:132) __x64_sys_unshare (kernel/fork.c:3316) do_syscall_64 (arch/x86/entry/syscall_64.c:63) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Freed by task 8: kfree (mm/slub.c:6566) tipc_exit_net (net/tipc/core.c:119) cleanup_net (net/core/net_namespace.c:704) process_one_work (kernel/workqueue.c:3314) kthread (kernel/kthread.c:436) This is the same class of bug that commit e279024617134 ("net/tipc: fix slab-use-after-free Read in tipc_aead_encrypt_done") fixed for the encrypt side. The encrypt path takes maybe_get_net(aead->crypto->net) before crypto_aead_encrypt() and drops it with put_net() on the synchronous return paths and in tipc_aead_encrypt_done(); the -EINPROGRESS/-EBUSY return keeps the reference for the async callback to release. The decrypt path was left without the equivalent guard. Mirror the encrypt-side fix on the decrypt path: take a net reference before crypto_aead_decrypt() (failing with -ENODEV and the matching bearer put if it cannot be acquired), keep it across the -EINPROGRESS/-EBUSY async return, and drop it with put_net() on the synchronous success/error return and at the end of tipc_aead_decrypt_done(). Reproduced under KASAN on v7.1-rc7: a UDP bearer with a cluster key is flooded with crafted encrypted frames from an unknown peer (driving the cluster-key decrypt path) while the bearer's netns is repeatedly torn down. The completion must run asynchronously to outlive tipc_crypto_stop(); on x86 the stock aesni gcm(aes) now decrypts synchronously, so the async path was exercised via cryptd offload. The unguarded aead->crypto dereference in tipc_aead_decrypt_done() is the unpatched upstream path; tipc_aead_decrypt() still lacks maybe_get_net(aead->crypto->net), so the completion can outlive the free on any config where crypto_aead_decrypt() goes async. Found by 0sec automated security-research tooling (https://0sec.ai).
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/0a780653b2a7569a7af9be7d0b00b1251baca63a
- git.kernel.org/stable/c/171d31245d11bf84836fad3b394cb465a4d008ec
- git.kernel.org/stable/c/1eea5e1820a2f5164d706bd1277bc97ff31ce32d
- git.kernel.org/stable/c/2d1f21419ec121232c916d3a3fc9b6766473a0e7
- git.kernel.org/stable/c/bda3348872a2ef0d19f2df6aa8cb5025adce2f20
- git.kernel.org/stable/c/dca7713fe044a2067387948557ea099056e1679e
- git.kernel.org/stable/c/e18769616fd5a90ec1e12aabbba544c488284292
- git.kernel.org/stable/c/eaca7dae02fab70c8d223cffe03cec1b93249ce2
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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