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CVE-2026-63979— net/handshake: hand off the pinned file reference to accept_doit

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 6.4版本存在安全漏洞，该漏洞源于握手请求处理中对文件引用管理不当，可能导致空指针读取或访问已释放内存。

CVSS 9.8 · Critical EPSS 0.61% · P48

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 3b3009ea8abb713b022d94fba95ec270cf6e7eae< 68eba6519cbd6359fb554a9720f3a3b6b2eba23f affected
3b3009ea8abb713b022d94fba95ec270cf6e7eae< c06876d4fac38f35820946ee3b1be7d7da799cd4 affected
3b3009ea8abb713b022d94fba95ec270cf6e7eae< f4251190e58b209999c1ba9e6d2976136a1be055 affected
6.4 affected
< 6.4 unaffected
6.18.44≤ 6.18.* unaffected
7.0.12≤ 7.0.* unaffected
7.1≤ * unaffected
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I. Basic Information for CVE-2026-63979

Vulnerability Information
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Vulnerability Title
net/handshake: hand off the pinned file reference to accept_doit
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/handshake: hand off the pinned file reference to accept_doit handshake_req_next() removes the request from the per-net pending list and drops hn_lock before handshake_nl_accept_doit() reads req->hr_sk->sk_socket and dereferences sock->file (once in FD_PREPARE() and again in get_file()). In that window a consumer running tls_handshake_cancel() followed by sockfd_put() (svc_sock_free) or __fput_sync() (xs_reset_transport) releases sock->file. sock_release() then runs sock_orphan(), zeroing sk_socket, and frees the struct socket. The accept-side code either reads NULL through sk_socket or chases freed memory. The submit-side sock_hold() does not prevent this. sk_refcnt protects struct sock, but struct socket and sock->file are independently refcounted via the file descriptor the consumer owns. Pinning sk leaves sock and sock->file unprotected. Retarget the accept-side dereferences at req->hr_file, which was pinned at submit time, instead of req->hr_sk->sk_socket->file. Pinning on its own is not sufficient: a consumer that cancels between handshake_req_next() returning and accept_doit reaching FD_PREPARE() takes the !remove_pending() branch in handshake_req_cancel() and drops hr_file before the accept side takes its own reference. Hand off an additional file reference inside handshake_req_next(), under hn_lock, so the accept side operates on a reference that no concurrent handshake_req_cancel() can revoke. FD_PREPARE() consumes that handed-off reference, either by transferring it to the new fd in fd_publish() or by dropping it in the cleanup destructor on error; the explicit get_file() that previously balanced FD_PREPARE() is therefore redundant and goes away. Update handshake_req_cancel_test2 and _test3 to simulate the FD_PREPARE() consumption with an fput() so the kunit file-count assertions stay balanced.
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 6.4版本存在安全漏洞，该漏洞源于握手请求处理中对文件引用管理不当，可能导致空指针读取或访问已释放内存。
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 3b3009ea8abb713b022d94fba95ec270cf6e7eae ~ 68eba6519cbd6359fb554a9720f3a3b6b2eba23f -
Linux Linux 6.4 -

II. Public POCs for CVE-2026-63979

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III. Intelligence Information for CVE-2026-63979

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Patches & Fixes for CVE-2026-63979 (2)

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-2026-64136 9.8 CRITICAL smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()
CVE-2026-63993 9.8 CRITICAL vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
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-2026-64091 9.8 CRITICAL batman-adv: tt: fix TOCTOU race for reported vlans
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-64055 9.8 CRITICAL net: ethernet: cortina: Carry over frag counter
CVE-2026-63924 9.8 CRITICAL ipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo()
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
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-2026-63888 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-2026-64056 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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