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CVE-2026-31422— net/sched: cls_flow: fix NULL pointer dereference on shared blocks

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cls_flow模块在共享块上存在空指针取消引用，可能导致内核崩溃。

AI Predicted 6.5 Difficulty: Moderate EPSS 0.17% · P6

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 1abf272022cf1d18469405f47b4ec49c6a3125db< 57f94ac7e953eece5ed4819605a18f3cdfc63dcc affected
1abf272022cf1d18469405f47b4ec49c6a3125db< 942813276edeb1741fa5b0a73471beb4e495fa08 affected
1abf272022cf1d18469405f47b4ec49c6a3125db< cc707a4fd4c3b6ab2722e06bc359aa010e13d408 affected
1abf272022cf1d18469405f47b4ec49c6a3125db< 4a09f72007201c9f667dc47f64517ec23eea65e5 affected
1abf272022cf1d18469405f47b4ec49c6a3125db< 9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e affected
1abf272022cf1d18469405f47b4ec49c6a3125db< a208c3e1232997e9317887294c20008dfcb75449 affected
1abf272022cf1d18469405f47b4ec49c6a3125db< 415ea0c973c754b9f375225807810eb9045f4293 affected
1abf272022cf1d18469405f47b4ec49c6a3125db< 1a280dd4bd1d616a01d6ffe0de284c907b555504 affected
… +10 more rows
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I. Basic Information for CVE-2026-31422

Vulnerability Information
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Vulnerability Title
net/sched: cls_flow: fix NULL pointer dereference on shared blocks
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: fix NULL pointer dereference on shared blocks flow_change() calls tcf_block_q() and dereferences q->handle to derive a default baseclass. Shared blocks leave block->q NULL, causing a NULL deref when a flow filter without a fully qualified baseclass is created on a shared block. Check tcf_block_shared() before accessing block->q and return -EINVAL for shared blocks. This avoids the null-deref shown below: ======================================================================= KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:flow_change (net/sched/cls_flow.c:508) Call Trace: tc_new_tfilter (net/sched/cls_api.c:2432) rtnetlink_rcv_msg (net/core/rtnetlink.c:6980) [...] =======================================================================
Source: CVE Program / CVE List V5
CVSS Information
N/A
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cls_flow模块在共享块上存在空指针取消引用，可能导致内核崩溃。
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 1abf272022cf1d18469405f47b4ec49c6a3125db ~ 57f94ac7e953eece5ed4819605a18f3cdfc63dcc -
Linux Linux 4.15 -

II. Public POCs for CVE-2026-31422

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III. Intelligence Information for CVE-2026-31422

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Same Patch Batch · Linux · 2026-04-13 · 15 CVEs total

CVE-2026-31414 9.8 CRITICAL netfilter: nf_conntrack_expect: use expect->helper
CVE-2026-31419 7.8 HIGH net: bonding: fix use-after-free in bond_xmit_broadcast()
CVE-2026-31417 7.5 HIGH net/x25: Fix overflow when accumulating packets
CVE-2026-31426 7.0 HIGH ACPI: EC: clean up handlers on probe failure in acpi_ec_setup()
CVE-2026-31428 netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD
CVE-2026-31427 netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp
CVE-2026-31425 rds: ib: reject FRMR registration before IB connection is established
CVE-2026-31424 netfilter: x_tables: restrict xt_check_match/xt_check_target extensions for NFPROTO_ARP
CVE-2026-31423 net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()
CVE-2026-31420 bridge: mrp: reject zero test interval to avoid OOM panic
CVE-2026-31421 net/sched: cls_fw: fix NULL pointer dereference on shared blocks
CVE-2026-31418 netfilter: ipset: drop logically empty buckets in mtype_del
CVE-2026-31416 netfilter: nfnetlink_log: account for netlink header size
CVE-2026-31415 ipv6: avoid overflows in ip6_datagram_send_ctl()

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31422

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