CVE-2025-39984 Vulnerability Analysis & Exploit Details

CVE-2025-39984
Vulnerability Scoring

Analysis In Progress

Attack Complexity Details

Attack Complexity:
Attack Complexity Analysis In Progress
Attack Vector:
Attack Vector Under Analysis
Privileges Required: None
No authentication is required for exploitation.
Scope:
Impact is confined to the initially vulnerable component.
User Interaction: None
No user interaction is necessary for exploitation.

CVE-2025-39984 Details

Status: Received on 15 Oct 2025, 08:15 UTC

Published on: 15 Oct 2025, 08:15 UTC

CVSS Release:

CVE-2025-39984 Vulnerability Summary

CVE-2025-39984: 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.

Assessing the Risk of CVE-2025-39984

Access Complexity Graph

The exploitability of CVE-2025-39984 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2025-39984

No exploitability data is available for CVE-2025-39984.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2025-39984, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2025-39984, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

Confidentiality: None
CVE-2025-39984 does not compromise confidentiality.
Integrity: None
CVE-2025-39984 does not impact data integrity.
Availability: None
CVE-2025-39984 does not affect system availability.

CVE-2025-39984 References

External References

CWE Common Weakness Enumeration

Unknown

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