Bug 2517051 (CVE-2026-74473)

Summary: CVE-2026-74473 kernel: vxlan: use pskb_network_may_pull() in route_shortcircuit()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Virtual Extensible LAN (VXLAN) implementation. An incorrect buffer length check in the `route_shortcircuit()` function, specifically when using `pskb_may_pull()`, can lead to reading beyond the allocated buffer length. This occurs when processing IP headers in non-linear network packet fragments. This vulnerability could potentially allow an attacker to access sensitive information or cause a denial of service.
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Description OSIDB Bzimport 2026-08-15 12:47:11 UTC 
In the Linux kernel, the following vulnerability has been resolved:

vxlan: use pskb_network_may_pull() in route_shortcircuit()

route_shortcircuit() currently calls pskb_may_pull(skb, sizeof(struct iphdr))
(or ipv6hdr), which checks if bytes are available starting from skb->data.

However, in vxlan_xmit(), skb->data points to the MAC header, so
skb_network_offset(skb) is ETH_HLEN (14 bytes). Using pskb_may_pull(skb, 20)
only checks 20 bytes from skb->data (which is 14 bytes MAC header + 6 bytes of
IP header), leaving the rest of the IP header potentially un-pulled in non-linear
frags. Subsequent dereferences of ip_hdr(skb)->daddr can read beyond the pulled
linear buffer length.

Fix this by using pskb_network_may_pull(), which adds skb_network_offset(skb) to
the length check to ensure the full network header is present in the linear buffer.
Comment 1 Mauro Matteo Cascella 2026-08-19 17:39:41 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081535-CVE-2026-74473-9c71@gregkh/T