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CVE-2026-63913— netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check

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 2.6.15版本存在安全漏洞，该漏洞源于netfilter conntrack tcp状态机未进行方向检查，导致无效序列号的RST数据包可将连接强制置为CLOSE状态，从而提前终止活跃的NAT连接。

CVSS 8.2 · High EPSS 0.97% · P59

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< 2006979a15af5404bf932a325357683c0bac1656 affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< 6476c17d536dbd321c073242e762ddb2713a1238 affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< f5547bebc416d56f56fb5b86dc20aabfa42165a0 affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< 2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77 affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< f206def4e86d810f927ba1d8e322ea72b29bce58 affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< b98ab51c45c5608a1c19ce7fd17a3032469bb83f affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< d67c6adee8d1b65330d0174c4c367faba14e80a8 affected
9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1< bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a affected
… +10 more rows
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I. Basic Information for CVE-2026-63913

Vulnerability Information
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Vulnerability Title
netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check An unintended behavior in the TCP conntrack state machine allows a connection to be forced into the CLOSE state using an RST packet with an invalid sequence number. Specifically, after a SYN packet is observed, an RST with an invalid SEQ can transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of whether the RST corresponds to the expected reply direction. The relevant code path assumes the RST is a response to an outgoing SYN, but does not validate packet direction or ensure that a matching SYN was actually sent in the opposite direction. As a result, a crafted packet sequence consisting of a SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry. This makes connection teardown easier than intended. So, tighten the state transition logic to ensure that RST-triggered CLOSE transitions only occur when the RST is a valid response to a previously observed SYN in the correct direction.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 2.6.15版本存在安全漏洞，该漏洞源于netfilter conntrack tcp状态机未进行方向检查，导致无效序列号的RST数据包可将连接强制置为CLOSE状态，从而提前终止活跃的NAT连接。
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 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ~ 2006979a15af5404bf932a325357683c0bac1656 -
Linux Linux 2.6.15 -

II. Public POCs for CVE-2026-63913

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III. Intelligence Information for CVE-2026-63913

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Patches & Fixes for CVE-2026-63913 (7)

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-2026-63922 9.8 CRITICAL ipv6: exthdrs: refresh nh after handling HAO option
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-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-63979 9.8 CRITICAL net/handshake: hand off the pinned file reference to accept_doit
CVE-2026-64056 9.8 CRITICAL net: ethernet: cortina: Make RX SKB per-port
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-63978 9.8 CRITICAL net/handshake: Drain pending requests at net namespace exit
CVE-2026-64055 9.8 CRITICAL net: ethernet: cortina: Carry over frag counter
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-63886 9.8 CRITICAL scsi: target: iscsi: Validate CHAP_R length before base64 decode
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-64035 9.8 CRITICAL igc: set tx buffer type for SMD frames
CVE-2026-64162 9.8 CRITICAL idpf: fix read_dev_clk_lock spinlock init in idpf_ptp_init()
CVE-2026-64150 9.8 CRITICAL netfilter: nft_inner: release local_lock before re-enabling softirqs
CVE-2026-64046 9.8 CRITICAL net: tls: prevent chain-after-chain in plain text SG

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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