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.
Analysis
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data available yet.
No vendor fix or workaround currently provided.
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Fri, 25 Sep 2026 10:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | vxlan: initialize _md in vxlan_xmit_one() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:23:07.952Z
Reserved: 2026-09-25T10:18:58.206Z
Link: CVE-2026-97965
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:24.293
Modified: 2026-09-25T11:17:24.293
Link: CVE-2026-97965
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.