CVE-2026-97965
UnknownSummary
In the Linux kernel, the vxlan_xmit_one() function in the VXLAN driver has an uninitialized stack variable _md when a VXLAN device has both VXLAN_F_COLLECT_METADATA and VXLAN_F_GBP enabled, and the transmitted packet lacks the IP_TUNNEL_VXLAN_OPT_BIT flag. This leads to reading garbage from the stack, which can spuriously set flags in the VXLAN header and leak 16 bits of uninitialized kernel data onto the wire.
Risk Assessment
The organization is exposed to kernel stack information leakage into the network, potentially revealing sensitive data. Additionally, incorrect flags in VXLAN headers may cause network malfunction or security issues in environments using VXLAN and GBP.
Recommendation
It is recommended to immediately update the Linux kernel to a version containing the fix that zero-initializes the _md variable. Also monitor distribution security advisories and apply the appropriate backport of the patch.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: vxlan: initialize _md in vxlan_xmit_one() If a VXLAN device is configured with both VXLAN_F_COLLECT_METADATA and VXLAN_F_GBP, and a packet is transmitted through it using an external ip_tunnel_info that lacks the IP_TUNNEL_VXLAN_OPT_BIT flag, md is left pointing to the uninitialized _md stack variable: if (test_bit(IP_TUNNEL_VXLAN_OPT_BIT, info->key.tun_flags)) { if (info->options_len < sizeof(*md)) goto drop; md = ip_tunnel_info_opts(info); } Because IP_TUNNEL_VXLAN_OPT_BIT is not set, md is not updated and remains pointing to _md. Later, vxlan_build_skb() is called with md, which eventually calls vxlan_build_gbp_hdr(): if (vxflags & VXLAN_F_GBP) vxlan_build_gbp_hdr(vxh, md); Inside vxlan_build_gbp_hdr(), md->gbp is read: if (!md->gbp) return; gbp = (struct vxlanhdr_gbp *)vxh; ... if (md->gbp & VXLAN_GBP_DONT_LEARN) gbp->dont_learn = 1; If the stack contains garbage, this causes: 1) VXLAN_HF_GBP flag to be spuriously set in the VXLAN header. 2) gbp->dont_learn and gbp->policy_applied to be set from stack bits. 3) gbp->policy_id to receive 16 bits of uninitialized kernel stack data, leaking it onto the wire. Fix this by zero-initializing _md. If IP_TUNNEL_VXLAN_OPT_BIT is not present, md->gbp remains 0, and vxlan_build_gbp_hdr() returns early without modifying the VXLAN header.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS