tun: zero the whole vnet header in tun_put_user()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-52940
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-24 08:16:24 UTC
Updated2026-07-08 19:12:57 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.001120000 probability, percentile 0.016440000 (date 2026-07-09)

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5 git Not specified
CNA Linux Linux affected 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 585cb85e9a29185be05f326369573c2663cf4380 git Not specified
CNA Linux Linux affected 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 7f2fcff15e99bb852f6967396ed12b38376e2c8d git Not specified
CNA Linux Linux affected 6.17 Not specified
CNA Linux Linux unaffected 6.17 semver Not specified
CNA Linux Linux unaffected 6.18.36 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.13 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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