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CVE-2026-64007— netfilter: synproxy: refresh tcphdr after skb_ensure_writable

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基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于在skb_ensure_writable之后未刷新tcphdr指针，可能导致写入已释放的内存或数据包校验和不匹配。

CVSS 9.8 · Critical EPSS 0.51% · P42

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 48b1de4c110a7afa4b85862f6c75af817db26fad< 9902a1058992de5d95656b64a3bd95c077f7ba2c affected
48b1de4c110a7afa4b85862f6c75af817db26fad< d3019c61799adc21811af4b521f11f3dc77f8e04 affected
48b1de4c110a7afa4b85862f6c75af817db26fad< dd206819f210522579010d889d45a9530bb494bc affected
48b1de4c110a7afa4b85862f6c75af817db26fad< af2c22ccb1f621aff487ff47a040e38e058541e7 affected
48b1de4c110a7afa4b85862f6c75af817db26fad< c7f945f7da097245a2f8ed7775ce48421047ee96 affected
48b1de4c110a7afa4b85862f6c75af817db26fad< f0fea2b6d5453a11ad11713bbf37561b9b3a7edf affected
48b1de4c110a7afa4b85862f6c75af817db26fad< a91887a5b6ee4b98dfbf1db657ed2b879430149e affected
48b1de4c110a7afa4b85862f6c75af817db26fad< 92170e6afe927ab2792a3f71902845789c8e31b1 affected
… +10 more rows
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I. Basic Information for CVE-2026-64007

Vulnerability Information
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Vulnerability Title
netfilter: synproxy: refresh tcphdr after skb_ensure_writable
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: refresh tcphdr after skb_ensure_writable synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer. Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale: caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */ The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload. Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/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基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于在skb_ensure_writable之后未刷新tcphdr指针，可能导致写入已释放的内存或数据包校验和不匹配。
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 48b1de4c110a7afa4b85862f6c75af817db26fad ~ 9902a1058992de5d95656b64a3bd95c077f7ba2c -
Linux Linux 3.12 -

II. Public POCs for CVE-2026-64007

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III. Intelligence Information for CVE-2026-64007

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Patches & Fixes for CVE-2026-64007 (8)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-63979 9.8 CRITICAL net/handshake: hand off the pinned file reference to accept_doit
CVE-2026-53399 9.8 CRITICAL nfsd: release layout stid on setlease failure
CVE-2026-53398 9.8 CRITICAL NFSD: Fix SECINFO_NO_NAME decode error cleanup
CVE-2026-64089 9.8 CRITICAL batman-adv: tt: fix negative last_changeset_len
CVE-2026-64025 9.8 CRITICAL bpf, skmsg: fix verdict sk_data_ready racing with ktls rx
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-63924 9.8 CRITICAL ipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo()
CVE-2026-64055 9.8 CRITICAL net: ethernet: cortina: Carry over frag counter
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-64037 9.8 CRITICAL wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-64136 9.8 CRITICAL smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()
CVE-2026-64056 9.8 CRITICAL net: ethernet: cortina: Make RX SKB per-port
CVE-2026-64061 9.8 CRITICAL netfs: Fix early put of sink folio in netfs_read_gaps()
CVE-2026-64125 9.8 CRITICAL net: bcmgenet: keep RBUF EEE/PM disabled
CVE-2026-64102 9.8 CRITICAL RDMA/siw: Reject MPA FPDU length underflow before signed receive math
CVE-2026-63825 9.8 CRITICAL gcov: use atomic counter updates to fix concurrent access crashes

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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