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CVE-2026-52940— tun: zero the whole vnet header in tun_put_user()

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基金会开源的操作系统Linux所使用的内核。 Linux kernel 6.17版本及之前版本存在安全漏洞，该漏洞源于tun_put_user函数中未初始化vnet header结构体，导致内核栈内存泄漏，可能允许无权限用户泄露14字节内核栈数据。

AI Predicted 5.5 Difficulty: Moderate EPSS 0.11% · P1

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37< 5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5 affected
288f30435132d2f9e7a29ec9b9745a4f9dc7fd37< 585cb85e9a29185be05f326369573c2663cf4380 affected
288f30435132d2f9e7a29ec9b9745a4f9dc7fd37< 7f2fcff15e99bb852f6967396ed12b38376e2c8d affected
6.17 affected
< 6.17 unaffected
6.18.36≤ 6.18.* unaffected
7.0.13≤ 7.0.* unaffected
7.1≤ * unaffected
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I. Basic Information for CVE-2026-52940

Vulnerability Information
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Vulnerability Title
tun: zero the whole vnet header in tun_put_user()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: tun: zero the whole vnet header in tun_put_user() tun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel without zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb() only initializes the first 10 bytes (sizeof(struct virtio_net_hdr)), leaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack garbage. An unprivileged user can set the vnet header size to 24 with TUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the partially-initialized struct to userspace, leaking 14 bytes of kernel stack on every read of a non-tunnel packet. Fix it the same way tun_get_user() already does by zeroing the whole header right after declaration.
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基金会开源的操作系统Linux所使用的内核。 Linux kernel 6.17版本及之前版本存在安全漏洞，该漏洞源于tun_put_user函数中未初始化vnet header结构体，导致内核栈内存泄漏，可能允许无权限用户泄露14字节内核栈数据。
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 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 ~ 5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5 -
Linux Linux 6.17 -

II. Public POCs for CVE-2026-52940

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III. Intelligence Information for CVE-2026-52940

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Patches & Fixes for CVE-2026-52940 (3)

Same Patch Batch · Linux · 2026-06-24 · 219 CVEs total

CVE-2026-53049 9.8 CRITICAL gfs2: add some missing log locking
CVE-2026-52993 9.8 CRITICAL tipc: fix double-free in tipc_buf_append()
CVE-2026-52989 9.8 CRITICAL nvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
CVE-2026-52986 9.8 CRITICAL netfilter: nf_conntrack_sip: don't use simple_strtoul
CVE-2026-52982 9.8 CRITICAL net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit()
CVE-2026-53002 9.8 CRITICAL netfilter: conntrack: remove sprintf usage
CVE-2026-53006 9.8 CRITICAL ipv6: fix possible UAF in icmpv6_rcv()
CVE-2026-53045 9.8 CRITICAL memory: tegra124-emc: Fix dll_change check
CVE-2026-53086 9.8 CRITICAL net: bcmgenet: fix racing timeout handler
CVE-2026-53046 9.8 CRITICAL ksmbd: fix use-after-free from async crypto on Qualcomm crypto engine
CVE-2026-52955 9.8 CRITICAL libceph: Fix potential out-of-bounds access in crush_decode()
CVE-2026-53010 9.8 CRITICAL ksmbd: fix use-after-free in smb2_open during durable reconnect
CVE-2026-53088 9.8 CRITICAL net: bcmgenet: fix off-by-one in bcmgenet_put_txcb
CVE-2026-52914 9.8 CRITICAL batman-adv: fix fragment reassembly length accounting
CVE-2026-53055 9.8 CRITICAL crypto: hisilicon/sec2 - prevent req used-after-free for sec
CVE-2026-52924 9.8 CRITICAL sctp: purge outqueue on stale COOKIE-ECHO handling
CVE-2026-52931 9.8 CRITICAL batman-adv: tp_meter: avoid use of uninit sender vars
CVE-2026-52999 9.1 CRITICAL netfilter: nfnetlink_osf: fix out-of-bounds read on option matching
CVE-2026-53043 9.1 CRITICAL ocfs2/dlm: validate qr_numregions in dlm_match_regions()
CVE-2026-52958 9.1 CRITICAL libceph: Fix potential out-of-bounds access in osdmap_decode()

Showing top 20 of 219 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-52940

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