EUVD-2026-86819
GHSA-qvvr-rf39-ch86
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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:
- VXLAN_HF_GBP flag to be spuriously set in the VXLAN header.
- gbp->dont_learn and gbp->policy_applied to be set from stack bits.
- 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.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
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