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Fencer Vulns
no cvss —

CVE-2025-39984 json

net: tun: Update napi->skb after XDP process

published 2025-10-15 12 mo ago modified 2026-10-19 20 d ago also EUVD-2025-34588

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: tun: Update napi->skb after XDP process

The syzbot report a UAF issue:

BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline] BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline] BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758 Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079 CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Call Trace: <TASK> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x240 mm/kasan/report.c:482 kasan_report+0x118/0x150 mm/kasan/report.c:595 skb_reset_mac_header include/linux/skbuff.h:3150 [inline] napi_frags_skb net/core/gro.c:723 [inline] napi_gro_frags+0x6e/0x1030 net/core/gro.c:758 tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x5c9/0xb30 fs/read_write.c:686 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK>

Allocated by task 6079: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:68 unpoison_slab_object mm/kasan/common.c:330 [inline] __kasan_mempool_unpoison_object+0xa0/0x170 mm/kasan/common.c:558 kasan_mempool_unpoison_object include/linux/kasan.h:388 [inline] napi_skb_cache_get+0x37b/0x6d0 net/core/skbuff.c:295 __alloc_skb+0x11e/0x2d0 net/core/skbuff.c:657 napi_alloc_skb+0x84/0x7d0 net/core/skbuff.c:811 napi_get_frags+0x69/0x140 net/core/gro.c:673 tun_napi_alloc_frags drivers/net/tun.c:1404 [inline] tun_get_user+0x77c/0x3e20 drivers/net/tun.c:1784 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x5c9/0xb30 fs/read_write.c:686 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6079: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576 poison_slab_object mm/kasan/common.c:243 [inline] __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2422 [inline] slab_free mm/slub.c:4695 [inline] kmem_cache_free+0x18f/0x400 mm/slub.c:4797 skb_pp_cow_data+0xdd8/0x13e0 net/core/skbuff.c:969 netif_skb_check_for_xdp net/core/dev.c:5390 [inline] netif_receive_generic_xdp net/core/dev.c:5431 [inline] do_xdp_generic+0x699/0x11a0 net/core/dev.c:5499 tun_get_user+0x2523/0x3e20 drivers/net/tun.c:1872 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x5c9/0xb30 fs/read_write.c:686 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

After commit e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in generic mode"), the original skb may be freed in skb_pp_cow_data() when XDP program was attached, which was allocated in tun_napi_alloc_frags(). However, the napi->skb still point to the original skb, update it after XDP process.

Patch / fix

  • Linux Linux 6.12.50, 6.16.10, 6.17
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.16.10-1

debian advisories DEBIAN-CVE-2025-39984

  • linux Ubuntu 25.10 6.17.0-6.6
  • linux-aws Ubuntu 25.10 6.17.0-1003.3
  • linux-gcp Ubuntu 25.10 6.17.0-1003.3
  • linux-azure Ubuntu 25.10 6.17.0-1006.6
  • linux-raspi Ubuntu 25.10 6.17.0-1004.4
  • linux-riscv Ubuntu 25.10 6.17.0-6.6.1
  • linux-oracle Ubuntu 25.10 6.17.0-1003.3
  • linux-realtime Ubuntu 25.10 6.17.0-1002.3

ubuntu advisories UBUNTU-CVE-2025-39984

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 10.1 6.12.0-124.21.1.el10_1
  • rv RHEL 10.1 6.12.0-124.21.1.el10_1
  • perf RHEL 10.1 6.12.0-124.21.1.el10_1
  • rtla RHEL 10.1 6.12.0-124.21.1.el10_1
  • libperf RHEL 10.1 6.12.0-124.21.1.el10_1
  • kernel-rt RHEL 10.1 6.12.0-124.21.1.el10_1
  • kernel-64k RHEL 10.1 6.12.0-124.21.1.el10_1
  • kernel-core RHEL 10.1 6.12.0-124.21.1.el10_1

red hat advisories RHSA-2025:23279RHSA-2025:23250

  • kernel-rt Linux Micro 6.2 6.12.0-160000.7.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.7.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.6.1.160000.2.4
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.7.1
  • kernel-kvmsmall SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.7.1

suse advisories SUSE-SU-2025:21080-1SUSE-SU-2025:21147-1SUSE-SU-2025:21180-1SUSE-SU-2026:20561-1SUSE-SU-2025:4141-1SUSE-SU-2025:4132-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.7.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.7.1

opensuse advisories openSUSE-SU-2025:20091-1

  • kernel-abi-stablelists AlmaLinux 10 6.12.0-124.21.1.el10_1

almalinux advisories ALSA-2025:23279

  • kernel Rocky Linux 10 6.12.0-124.21.1.el10_1

rocky linux advisories RLSA-2025:23279

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-39984 updated cvss 7.3

kernel: net: tun: Update napi->skb after XDP process

  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-124.21.1.el10_1, perf 6.12.0-124.21.1.el10_1, rtla 6.12.0-124.21.1.el10_1, python3-perf 6.12.0-124.21.1.el10_1, kernel-devel-matched 6.12.0-124.21.1.el10_1, kernel-64k-devel-matched 6.12.0-124.21.1.el10_1, +7 more
    fixed: vendor fix RHSA-2025:23279
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.50.1.el10_0, perf 6.12.0-55.50.1.el10_0, rtla 6.12.0-55.50.1.el10_0, python3-perf 6.12.0-55.50.1.el10_0, kernel-devel-matched 6.12.0-55.50.1.el10_0, kernel-64k-devel-matched 6.12.0-55.50.1.el10_0, +7 more
    fixed: vendor fix RHSA-2025:23250
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-124.21.1.el10_1, kernel-64k 6.12.0-124.21.1.el10_1, kernel-core 6.12.0-124.21.1.el10_1, kernel-tools 6.12.0-124.21.1.el10_1, kernel-modules 6.12.0-124.21.1.el10_1, kernel-64k-core 6.12.0-124.21.1.el10_1, +28 more
    fixed: vendor fix RHSA-2025:23279
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.50.1.el10_0, kernel-64k 6.12.0-55.50.1.el10_0, kernel-core 6.12.0-55.50.1.el10_0, kernel-tools 6.12.0-55.50.1.el10_0, kernel-modules 6.12.0-55.50.1.el10_0, kernel-64k-core 6.12.0-55.50.1.el10_0, +27 more
    fixed: vendor fix RHSA-2025:23250
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-124.21.1.el10_1, kernel-debuginfo-common-s390x 6.12.0-124.21.1.el10_1, kernel-debuginfo-common-x86_64 6.12.0-124.21.1.el10_1, kernel-debuginfo-common-aarch64 6.12.0-124.21.1.el10_1, kernel-debuginfo-common-ppc64le 6.12.0-124.21.1.el10_1
    fixed: vendor fix RHSA-2025:23279
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.50.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.50.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.50.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.50.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.50.1.el10_0
    fixed: vendor fix RHSA-2025:23250
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-124.21.1.el10_1, kernel-rt-64k 6.12.0-124.21.1.el10_1, kernel-rt-core 6.12.0-124.21.1.el10_1, kernel-rt-modules 6.12.0-124.21.1.el10_1, kernel-rt-64k-core 6.12.0-124.21.1.el10_1, kernel-rt-debug-core 6.12.0-124.21.1.el10_1, +14 more
    fixed: vendor fix RHSA-2025:23279
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.50.1.el10_0, kernel-rt-64k 6.12.0-55.50.1.el10_0, kernel-rt-core 6.12.0-55.50.1.el10_0, kernel-rt-modules 6.12.0-55.50.1.el10_0, kernel-rt-64k-core 6.12.0-55.50.1.el10_0, kernel-rt-debug-core 6.12.0-55.50.1.el10_0, +14 more
    fixed: vendor fix RHSA-2025:23250
show 3 more
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-124.21.1.el10_1, kernel-rt-core 6.12.0-124.21.1.el10_1, kernel-rt-modules 6.12.0-124.21.1.el10_1, kernel-rt-debug-core 6.12.0-124.21.1.el10_1, kernel-rt-modules-core 6.12.0-124.21.1.el10_1, kernel-rt-debug-modules 6.12.0-124.21.1.el10_1, +4 more
    fixed: vendor fix RHSA-2025:23279
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.50.1.el10_0, kernel-rt-kvm 6.12.0-55.50.1.el10_0, kernel-rt-core 6.12.0-55.50.1.el10_0, kernel-rt-modules 6.12.0-55.50.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.50.1.el10_0, kernel-rt-debug-core 6.12.0-55.50.1.el10_0, +6 more
    fixed: vendor fix RHSA-2025:23250
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.