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CVE-2026-31504— net: fix fanout UAF in packet_release() via NETDEV_UP race

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NETDEV_UP竞争条件导致fanout释放后重用，可能导致数据包释放时出现悬空指针。

CVSS 7.8 · High EPSS 0.14% · P3

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux ce06b03e60fc19c680d1bf873e779bf11c2fc518< ee642b1962caa9aa231c01abbd58bc453ae6b66e affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< 42cfd7898eeed290c9fb73f732af1f7d6b0a703e affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< 1b4c03f8892d955385c202009af7485364731bb9 affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< 654386baef228c2992dbf604c819e4c7c35fc71b affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< 75fe6db23705a1d55160081f7b37db9665b1880b affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6 affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< ceccbfc6de720ad633519a226715989cfb065af1 affected
ce06b03e60fc19c680d1bf873e779bf11c2fc518< 42156f93d123436f2a27c468f18c966b7e5db796 affected
… +10 more rows
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I. Basic Information for CVE-2026-31504

Vulnerability Information
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Vulnerability Title
net: fix fanout UAF in packet_release() via NETDEV_UP race
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: fix fanout UAF in packet_release() via NETDEV_UP race `packet_release()` has a race window where `NETDEV_UP` can re-register a socket into a fanout group's `arr[]` array. The re-registration is not cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout array. `packet_release()` does NOT zero `po->num` in its `bind_lock` section. After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex` still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)` that already found the socket in `sklist` can re-register the hook. For fanout sockets, this re-registration calls `__fanout_link(sk, po)` which adds the socket back into `f->arr[]` and increments `f->num_members`, but does NOT increment `f->sk_ref`. The fix sets `po->num` to zero in `packet_release` while `bind_lock` is held to prevent NETDEV_UP from linking, preventing the race window. This bug was found following an additional audit with Claude Code based on CVE-2025-38617.
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NETDEV_UP竞争条件导致fanout释放后重用，可能导致数据包释放时出现悬空指针。
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

Vendor Product Affected Versions CPE Subscribe
Linux Linux ce06b03e60fc19c680d1bf873e779bf11c2fc518 ~ ee642b1962caa9aa231c01abbd58bc453ae6b66e -
Linux Linux 3.1 -

II. Public POCs for CVE-2026-31504

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III. Intelligence Information for CVE-2026-31504

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Same Patch Batch · Linux · 2026-04-22 · 100 CVEs total

CVE-2026-31478 9.8 CRITICAL ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()
CVE-2026-31463 9.8 CRITICAL iomap: fix invalid folio access when i_blkbits differs from I/O granularity
CVE-2026-31444 9.8 CRITICAL ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
CVE-2026-31436 9.8 CRITICAL dmaengine: idxd: fix possible wrong descriptor completion in llist_abort_desc()
CVE-2026-31501 9.8 CRITICAL net: ti: icssg-prueth: fix use-after-free of CPPI descriptor in RX path
CVE-2026-31448 9.4 CRITICAL ext4: avoid infinite loops caused by residual data
CVE-2026-31450 8.8 HIGH ext4: publish jinode after initialization
CVE-2026-31432 8.8 HIGH ksmbd: fix OOB write in QUERY_INFO for compound requests
CVE-2026-31433 8.8 HIGH ksmbd: fix potencial OOB in get_file_all_info() for compound requests
CVE-2026-31435 8.8 HIGH netfs: Fix read abandonment during retry
CVE-2026-31476 8.2 HIGH ksmbd: do not expire session on binding failure
CVE-2026-31464 8.1 HIGH scsi: ibmvfc: Fix OOB access in ibmvfc_discover_targets_done()
CVE-2026-31513 8.1 HIGH Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req
CVE-2026-31488 7.8 HIGH drm/amd/display: Do not skip unrelated mode changes in DSC validation
CVE-2026-31494 7.8 HIGH net: macb: use the current queue number for stats
CVE-2026-31454 7.8 HIGH xfs: save ailp before dropping the AIL lock in push callbacks
CVE-2026-31502 7.8 HIGH team: fix header_ops type confusion with non-Ethernet ports
CVE-2026-31479 7.8 HIGH drm/xe: always keep track of remap prev/next
CVE-2026-31505 7.8 HIGH iavf: fix out-of-bounds writes in iavf_get_ethtool_stats()
CVE-2026-31446 7.8 HIGH ext4: fix use-after-free in update_super_work when racing with umount

Showing top 20 of 100 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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