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CVE-2025-38666: net: appletalk: Fix use-after-free in AARP proxy probe

In the Linux kernel, the following vulnerability has been resolved: net: appletalk: Fix use-after-free in AARP proxy probe The AARP proxy‐probe routine (aarp_proxy_probe_network) sends a probe, releases the aarp_lock, sleeps, then re-acquires the lock. During that window an expire timer thread (__aarp_expire_timer) can remove and kfree() the same entry, leading to a use-after-free. race condition: cpu 0 | cpu 1 atalk_sendmsg() | atif_proxy_probe_device() aarp_send_ddp() | aarp_proxy_probe_network() mod_timer() | lock(aarp_lock) // LOCK!! timeout around 200ms | alloc(aarp_entry) and then call | proxies[hash] = aarp_entry aarp_expire_timeout() | aarp_send_probe() | unlock(aarp_lock) // UNLOCK!! lock(aarp_lock) // LOCK!! | msleep(100); __aarp_expire_timer(&proxies[ct]) | free(aarp_entry) | unlock(aarp_lock) // UNLOCK!! | | lock(aarp_lock) // LOCK!! | UAF aarp_entry !! ================================================================== BUG: KASAN: slab-use-after-free in aarp_proxy_probe_network+0x560/0x630 net/appletalk/aarp.c:493 Read of size 4 at addr ffff8880123aa360 by task repro/13278 CPU: 3 UID: 0 PID: 13278 Comm: repro Not tainted 6.15.2 #3 PREEMPT(full) Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc1/0x630 mm/kasan/report.c:521 kasan_report+0xca/0x100 mm/kasan/report.c:634 aarp_proxy_probe_network+0x560/0x630 net/appletalk/aarp.c:493 atif_proxy_probe_device net/appletalk/ddp.c:332 [inline] atif_ioctl+0xb58/0x16c0 net/appletalk/ddp.c:857 atalk_ioctl+0x198/0x2f0 net/appletalk/ddp.c:1818 sock_do_ioctl+0xdc/0x260 net/socket.c:1190 sock_ioctl+0x239/0x6a0 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl fs/ioctl.c:892 [inline] __x64_sys_ioctl+0x194/0x200 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcb/0x250 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> Allocated: aarp_alloc net/appletalk/aarp.c:382 [inline] aarp_proxy_probe_network+0xd8/0x630 net/appletalk/aarp.c:468 atif_proxy_probe_device net/appletalk/ddp.c:332 [inline] atif_ioctl+0xb58/0x16c0 net/appletalk/ddp.c:857 atalk_ioctl+0x198/0x2f0 net/appletalk/ddp.c:1818 Freed: kfree+0x148/0x4d0 mm/slub.c:4841 __aarp_expire net/appletalk/aarp.c:90 [inline] __aarp_expire_timer net/appletalk/aarp.c:261 [inline] aarp_expire_timeout+0x480/0x6e0 net/appletalk/aarp.c:317 The buggy address belongs to the object at ffff8880123aa300 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 96 bytes inside of freed 192-byte region [ffff8880123aa300, ffff8880123aa3c0) Memory state around the buggy address: ffff8880123aa200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8880123aa280: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc >ffff8880123aa300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880123aa380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff8880123aa400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ==================================================================

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-38666 is a Linux kernel memory-safety bug in the legacy AppleTalk AARP proxy-probe path. A race can let one kernel thread free an AppleTalk address entry while another still reads it. That can crash or corrupt kernel memory on systems where this AppleTalk code path is reachable. Public sources do not show active exploitation.

Executive priority

Treat this as a targeted kernel maintenance issue, not an emergency based on current evidence. Patch affected Linux fleets through normal accelerated kernel update channels, especially where AppleTalk is enabled or legacy networking is still present.

Technical view

The bug is a use-after-free in aarp_proxy_probe_network. The routine sends an AARP probe, drops aarp_lock, sleeps, then reacquires the lock. During that window, __aarp_expire_timer can remove and kfree the same aarp_entry. The provided KASAN trace shows slab-use-after-free in net/appletalk/aarp.c through the AppleTalk ioctl path.

Likely exposure

Exposure appears limited to Linux systems with AppleTalk support present and the AARP proxy-probe path reachable. AppleTalk is a legacy protocol, so typical modern deployments may have low exposure, but kernels or distributions carrying the affected code should still be checked.

Exploitation context

The source bundle provides a reproducible race trace and kernel stack, but no public exploit claim, CVSS score, or KEV listing. Privilege requirements are not stated in the provided sources, so exploitation reachability should be validated per kernel configuration and local policy.

Researcher notes

Key uncertainty is reachability. The trace shows an ioctl-driven AppleTalk path and a timer race, but the provided material does not define required capabilities, namespace constraints, or exploitability beyond KASAN-confirmed use-after-free. Validate against kernel config, module state, and downstream backports.

Mitigation direction

  • Apply Linux stable kernel updates containing the referenced fixes.
  • Apply Debian LTS kernel updates where applicable.
  • Disable or remove AppleTalk support if not required.
  • Check vendor advisories for exact fixed package versions.
  • Prioritize hosts exposing legacy AppleTalk functionality or custom kernels.

Validation and detection

  • Inventory kernels for AppleTalk support and loaded modules.
  • Compare running kernel versions against vendor-fixed releases.
  • Review distribution advisories for CVE-2025-38666 coverage.
  • Confirm the stable fix commit is present in custom kernels.
  • Document whether AppleTalk is required in each environment.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

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0CVSS vectors
3Timeline events
1ADP providers
11Source links

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  2. CVE publishedCVE Program

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Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 5.4.297, 5.10.241, 5.15.190, 6.1.148, 6.6.101, 6.12.41, 6.15.9, 6.16affected
Weakness

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