Bug 2460676 (CVE-2026-31472)

Summary: CVE-2026-31472 kernel: xfrm: iptfs: validate inner IPv4 header length in IPTFS payload
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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OS: Linux   
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A flaw was found in the Linux kernel, specifically within the xfrm and iptfs components. A remote attacker could exploit this vulnerability by sending a specially crafted Encapsulating Security Payload (ESP) packet. This packet, containing an inner IPv4 header with a total length (tot_len) of zero or malformed Internet Header Length (ihl) values, could trigger an infinite loop in the kernel's processing. This issue results in a Denial of Service (DoS), rendering the affected system unresponsive.
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Description OSIDB Bzimport 2026-04-22 15:04:48 UTC 
In the Linux kernel, the following vulnerability has been resolved:

xfrm: iptfs: validate inner IPv4 header length in IPTFS payload

Add validation of the inner IPv4 packet tot_len and ihl fields parsed
from decrypted IPTFS payloads in __input_process_payload(). A crafted
ESP packet containing an inner IPv4 header with tot_len=0 causes an
infinite loop: iplen=0 leads to capturelen=min(0, remaining)=0, so the
data offset never advances and the while(data < tail) loop never
terminates, spinning forever in softirq context.

Reject inner IPv4 packets where tot_len < ihl*4 or ihl*4 < sizeof(struct
iphdr), which catches both the tot_len=0 case and malformed ihl values.
The normal IP stack performs this validation in ip_rcv_core(), but IPTFS
extracts and processes inner packets before they reach that layer.
Comment 1 Keith Grant 2026-04-22 18:17:05 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042255-CVE-2026-31472-396d@gregkh/T