Description
In the Linux kernel, the following vulnerability has been resolved:

xfrm: iptfs: fix stack OOB read in iptfs_skb_reset_frag_walk()

iptfs_skb_reset_frag_walk() advances to the fragment containing @offset
with an unbounded loop:

while (offset >= walk->past + walk->frags[walk->fragi].len)
walk->past += walk->frags[walk->fragi++].len;

walk->fragi is advanced and walk->frags[walk->fragi] is dereferenced
without ever checking fragi against walk->nr_frags. When the requested
offset is at or beyond the total length spanned by the walk's fragments,
fragi runs past nr_frags and off the end of the fixed-size on-stack
frags[MAX_SKB_FRAGS + 1] array, reading out-of-bounds stack memory.

The two callers behave differently: iptfs_skb_add_frags() already guards
against this with

if (!walk->nr_frags ||
offset >= walk->total + walk->initial_offset)
return len;

but iptfs_skb_can_add_frags() has no such guard and calls
iptfs_skb_reset_frag_walk() unconditionally, so it performs the
out-of-range walk. Its own "fragi < walk->nr_frags" bound check runs only
afterwards, too late to prevent the read.

This is reachable from the receive path: a crafted IP-TFS (AGGFRAG)
payload delivered to an IPTFS SA drives iptfs_reassem_cont() ->
iptfs_skb_can_add_frags() with an offset past the fragment total, e.g.:

BUG: KASAN: stack-out-of-bounds in iptfs_skb_reset_frag_walk+0x235/0x250
Read of size 4 at addr ffff888008ad7210 by task repro/345
iptfs_skb_reset_frag_walk+0x235/0x250 net/xfrm/xfrm_iptfs.c:392
iptfs_skb_can_add_frags+0x155/0x310 net/xfrm/xfrm_iptfs.c:420
iptfs_reassem_cont+0xcf8/0x1140 net/xfrm/xfrm_iptfs.c:902
iptfs_input_ordered+0x552/0x670 net/xfrm/xfrm_iptfs.c:1280
iptfs_input+0x3d6/0xde0 net/xfrm/xfrm_iptfs.c:1741
xfrm_input+0x282f/0x6140 net/xfrm/xfrm_input.c:700
xfrm4_esp_rcv+0x93/0x120 net/ipv4/xfrm4_protocol.c:104
ip_rcv+0x278/0x2d0 net/ipv4/ip_input.c:612

Give iptfs_skb_can_add_frags() the same up-front guard that
iptfs_skb_add_frags() already has, so the walk is never entered with an
out-of-range offset. When it triggers, the caller falls back to the
existing linearize-and-copy path, which is safe.
Published: 2026-10-06
Score: n/a
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Tue, 06 Oct 2026 21:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125

Tue, 06 Oct 2026 18:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119
CWE-788

Tue, 06 Oct 2026 14:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119
CWE-788

Tue, 06 Oct 2026 09:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: xfrm: iptfs: fix stack OOB read in iptfs_skb_reset_frag_walk() iptfs_skb_reset_frag_walk() advances to the fragment containing @offset with an unbounded loop: while (offset >= walk->past + walk->frags[walk->fragi].len) walk->past += walk->frags[walk->fragi++].len; walk->fragi is advanced and walk->frags[walk->fragi] is dereferenced without ever checking fragi against walk->nr_frags. When the requested offset is at or beyond the total length spanned by the walk's fragments, fragi runs past nr_frags and off the end of the fixed-size on-stack frags[MAX_SKB_FRAGS + 1] array, reading out-of-bounds stack memory. The two callers behave differently: iptfs_skb_add_frags() already guards against this with if (!walk->nr_frags || offset >= walk->total + walk->initial_offset) return len; but iptfs_skb_can_add_frags() has no such guard and calls iptfs_skb_reset_frag_walk() unconditionally, so it performs the out-of-range walk. Its own "fragi < walk->nr_frags" bound check runs only afterwards, too late to prevent the read. This is reachable from the receive path: a crafted IP-TFS (AGGFRAG) payload delivered to an IPTFS SA drives iptfs_reassem_cont() -> iptfs_skb_can_add_frags() with an offset past the fragment total, e.g.: BUG: KASAN: stack-out-of-bounds in iptfs_skb_reset_frag_walk+0x235/0x250 Read of size 4 at addr ffff888008ad7210 by task repro/345 iptfs_skb_reset_frag_walk+0x235/0x250 net/xfrm/xfrm_iptfs.c:392 iptfs_skb_can_add_frags+0x155/0x310 net/xfrm/xfrm_iptfs.c:420 iptfs_reassem_cont+0xcf8/0x1140 net/xfrm/xfrm_iptfs.c:902 iptfs_input_ordered+0x552/0x670 net/xfrm/xfrm_iptfs.c:1280 iptfs_input+0x3d6/0xde0 net/xfrm/xfrm_iptfs.c:1741 xfrm_input+0x282f/0x6140 net/xfrm/xfrm_input.c:700 xfrm4_esp_rcv+0x93/0x120 net/ipv4/xfrm4_protocol.c:104 ip_rcv+0x278/0x2d0 net/ipv4/ip_input.c:612 Give iptfs_skb_can_add_frags() the same up-front guard that iptfs_skb_add_frags() already has, so the walk is never entered with an out-of-range offset. When it triggers, the caller falls back to the existing linearize-and-copy path, which is safe.
Title xfrm: iptfs: fix stack OOB read in iptfs_skb_reset_frag_walk()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-06T08:46:56.529Z

Reserved: 2026-09-25T10:25:14.345Z

Link: CVE-2026-98372

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-06T09:18:31.743

Modified: 2026-10-06T09:18:31.743

Link: CVE-2026-98372

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-06T20:45:06Z

Weaknesses