CVE-2026-43009— bpf: Fix incorrect pruning due to atomic fetch precision tracking
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于bpf回溯跟踪未正确处理原子获取操作，可能导致路径修剪错误。
Possible ATT&CK Techniques 2 AI
T1068 · Exploitation for Privilege Escalation T1190 · Exploit Public-Facing ApplicationAffected Version Matrix 8
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 5ca419f2864a2c60940dcf4bbaeb69546200e36f< ea150ffa9fc9f78c5cf22e1f7b06b6d016b1017c |
affected |
5ca419f2864a2c60940dcf4bbaeb69546200e36f< 7ffbe45b1d227e24659998a91cfd4c27af457e71 |
affected | ||
5ca419f2864a2c60940dcf4bbaeb69546200e36f< 179ee84a89114b854ac2dd1d293633a7f6c8dac1 |
affected | ||
5.12 |
affected | ||
< 5.12 |
unaffected | ||
6.18.50≤ 6.18.* |
unaffected | ||
6.19.12≤ 6.19.* |
unaffected | ||
7.0≤ * |
unaffected |
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I. Basic Information for CVE-2026-43009
Vulnerability Information
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Vulnerability Title
bpf: Fix incorrect pruning due to atomic fetch precision tracking
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix incorrect pruning due to atomic fetch precision tracking
When backtrack_insn encounters a BPF_STX instruction with BPF_ATOMIC
and BPF_FETCH, the src register (or r0 for BPF_CMPXCHG) also acts as
a destination, thus receiving the old value from the memory location.
The current backtracking logic does not account for this. It treats
atomic fetch operations the same as regular stores where the src
register is only an input. This leads the backtrack_insn to fail to
propagate precision to the stack location, which is then not marked
as precise!
Later, the verifier's path pruning can incorrectly consider two states
equivalent when they differ in terms of stack state. Meaning, two
branches can be treated as equivalent and thus get pruned when they
should not be seen as such.
Fix it as follows: Extend the BPF_LDX handling in backtrack_insn to
also cover atomic fetch operations via is_atomic_fetch_insn() helper.
When the fetch dst register is being tracked for precision, clear it,
and propagate precision over to the stack slot. For non-stack memory,
the precision walk stops at the atomic instruction, same as regular
BPF_LDX. This covers all fetch variants.
Before:
0: (b7) r1 = 8 ; R1=8
1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8
2: (b7) r2 = 0 ; R2=0
3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm
4: (bf) r3 = r10 ; R3=fp0 R10=fp0
5: (0f) r3 += r2
mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1
mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10
mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2)
mark_precise: frame0: regs=r2 stack= before 2: (b7) r2 = 0
6: R2=8 R3=fp8
6: (b7) r0 = 0 ; R0=0
7: (95) exit
After:
0: (b7) r1 = 8 ; R1=8
1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8
2: (b7) r2 = 0 ; R2=0
3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm
4: (bf) r3 = r10 ; R3=fp0 R10=fp0
5: (0f) r3 += r2
mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1
mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10
mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2)
mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0
mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1
mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8
6: R2=8 R3=fp8
6: (b7) r0 = 0 ; R0=0
7: (95) exit
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于bpf回溯跟踪未正确处理原子获取操作，可能导致路径修剪错误。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-43009
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-43009 (3)
Same Patch Batch · Linux · 2026-05-01 · 146 CVEs total
| CVE-2026-43037 | 9.8 CRITICAL | ip6_tunnel: clear skb2->cb[] in ip4ip6_err() |
| CVE-2026-43011 | 9.8 CRITICAL | net/x25: Fix potential double free of skb |
| CVE-2026-31705 | 9.8 CRITICAL | ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment |
| CVE-2026-43038 | 9.8 CRITICAL | ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() |
| CVE-2026-43039 | 9.8 CRITICAL | net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch |
| CVE-2026-31718 | 9.8 CRITICAL | ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger |
| CVE-2026-43018 | 8.8 HIGH | Bluetooth: hci_event: fix potential UAF in hci_le_remote_conn_param_req_evt |
| CVE-2026-31739 | 8.8 HIGH | crypto: tegra - Add missing CRYPTO_ALG_ASYNC |
| CVE-2026-31706 | 8.8 HIGH | ksmbd: validate num_aces and harden ACE walk in smb_inherit_dacl() |
| CVE-2026-31709 | 8.8 HIGH | smb: client: validate the whole DACL before rewriting it in cifsacl |
| CVE-2026-43048 | 8.8 HIGH | HID: core: Mitigate potential OOB by removing bogus memset() |
| CVE-2026-31735 | 8.8 HIGH | iommupt: Fix short gather if the unmap goes into a large mapping |
| CVE-2026-31773 | 8.8 HIGH | Bluetooth: SMP: derive legacy responder STK authentication from MITM state |
| CVE-2026-31717 | 8.8 HIGH | ksmbd: validate owner of durable handle on reconnect |
| CVE-2026-31712 | 8.3 HIGH | ksmbd: require minimum ACE size in smb_check_perm_dacl() |
| CVE-2026-31771 | 8.1 HIGH | Bluetooth: hci_event: move wake reason storage into validated event handlers |
| CVE-2026-43051 | 8.1 HIGH | HID: wacom: fix out-of-bounds read in wacom_intuos_bt_irq |
| CVE-2026-31708 | 8.1 HIGH | smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path |
| CVE-2026-31779 | 8.1 HIGH | wifi: iwlwifi: mvm: fix potential out-of-bounds read in iwl_mvm_nd_match_info_handler() |
| CVE-2026-43019 | 7.8 HIGH | Bluetooth: hci_conn: fix potential UAF in set_cig_params_sync |
Showing top 20 of 146 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Linux
-
CVE-2026-98868
dm-pcache: reject a kset that overruns its segment -
CVE-2026-98867
dm-pcache: bound the logical key offset from persistent memo -
CVE-2026-98866
sched/cache: Introduce task_struct->sched_cache_grp to fix U -
CVE-2026-98865
sched_ext: Don't run ops.dequeue() with a DSQ lock held -
CVE-2026-98864
sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing
Same vendor: Linux
-
CVE-2026-98868
dm-pcache: reject a kset that overruns its segment -
CVE-2026-98867
dm-pcache: bound the logical key offset from persistent memo -
CVE-2026-98866
sched/cache: Introduce task_struct->sched_cache_grp to fix U -
CVE-2026-98865
sched_ext: Don't run ops.dequeue() with a DSQ lock held -
CVE-2026-98864
sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing
V. Comments for CVE-2026-43009
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