Bug 2401489 (CVE-2023-53559)

Summary: CVE-2023-53559 kernel: ip_vti: fix potential slab-use-after-free in decode_session6
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A use-after-free flaw was found in the Linux kernel's ip_vti (IPsec Virtual Tunnel Interface) implementation when transmitting IPv6 packets with the SFB qdisc attached. A local user with CAP_NET_ADMIN capability can trigger this issue by configuring an ip_vti interface with an SFB qdisc and sending IPv6 traffic, causing the socket buffer control block to be modified during packet enqueuing and subsequently accessed after potential freeing during session decoding. This results in slab use-after-free, leading to kernel panic or potential memory corruption.
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Description OSIDB Bzimport 2025-10-04 16:03:30 UTC
In the Linux kernel, the following vulnerability has been resolved:

ip_vti: fix potential slab-use-after-free in decode_session6

When ip_vti device is set to the qdisc of the sfb type, the cb field
of the sent skb may be modified during enqueuing. Then,
slab-use-after-free may occur when ip_vti device sends IPv6 packets.
As commit f855691975bb ("xfrm6: Fix the nexthdr offset in
_decode_session6.") showed, xfrm_decode_session was originally intended
only for the receive path. IP6CB(skb)->nhoff is not set during
transmission. Therefore, set the cb field in the skb to 0 before
sending packets.