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CVE-2026-52940Disclosure(linux / linux_kernel)

LOWCVSS 5.5 · MEDIUM

Exploit discussion active in current signal (3 latest mentions)

Immediate actions

  • Hunt for exploitation attempts and persistence artifacts
  • Increase monitoring for publicly documented tradecraft
  • Track advisory updates for patch or workaround availability

Recommended action window: High priority (within 72h)

NVD 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.

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1.5/ 10 priority

Sources & remediation

Patch / fix

Priority

LOW

Exploitation

NONE

PoC

YES

Patch

AVAILABLE

Momentum

NONE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

  • linux_kernel

Threat summary

  • Public PoC is present in monitored signal
  • 3 mentions across 1 observed day

What's happening

  • PoC mentioned or linked in 1 signal
  • Technical details provided in 2 signals
  • Disclosure: 2 classified signals
  • Patch: 1 classified signal
  • 3 total mentions across 1 day

Affected systems

Vendors
linux
Products
linux_kernel

1 version affected across 1 product

Deep dive

Activity timeline3 mentions / 1d
01223Mentions · 2026-06-24: 3PoC Mentioned / Linked · 2026-06-24: 1Technical Details · 2026-06-24: 206-24
Signal classification2 categories
Disclosure
266.7%
Patch
133.3%
Referenced assets3 URLs
Full discourse3 posts
  • Infoflowcloud@infoflowcloud
    Disclosure

    🚨*CVE* CVE-2026-52940 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 vir… https://www.cve.org/CVERecord?id=CVE-2026-52940 ----- Traducción: CVE-2026-52940 En … http://infoflow.cloud`

    Post summary

    The post announces the discovery and resolution of CVE-2026-52940 in the Linux kernel, providing a brief technical description but no evidence of exploitation or mitigation steps.

    0000057
    88 followersView on X
  • CVE@CVEnew
    Patch

    CVE-2026-52940 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 vir… https://www.cve.org/CVERecord?id=CVE-2026-52940

    Post summary

    The CVE-2026-52940 bug in the Linux kernel's tun module has been remediated; the record provides minimal technical details but no PoC or exploit code.

    00000885
    57.7K followersView on X
  • VulDB 🛡@vuldb
    Disclosure

    There is a new vulnerability with elevated criticality in Linux Kernel (CVE-2026-52940) https://vuldb.com/vuln/373201

    Post summary

    A new critical Linux Kernel vulnerability (CVE-2026-52940) has been announced, with a link provided for additional information.

    0000093
    2.2K followersView on X
CPE platform detail8 entries

8 of 8 entries

PartVendorProductVersionTarget SWTarget HW
OSlinuxlinux_kernel---
OSlinuxlinux_kernel7.1--
OSlinuxlinux_kernel7.1--
OSlinuxlinux_kernel7.1--
OSlinuxlinux_kernel7.1--
OSlinuxlinux_kernel7.1--
OSlinuxlinux_kernel7.1--
OSlinuxlinux_kernel7.1--

Explore more

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