xfrm: iptfs: fix use-after-free on first_skb in __input_process_payload_CVE-2026-53240

8.8 / 10

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Description

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

xfrm: iptfs: fix use-after-free on first_skb in __input_process_payload

__input_process_payload() stores first_skb into xtfs->ra_newskb under
drop_lock when starting partial reassembly, then unlocks and breaks out
of the processing loop. The post-loop check reads xtfs->ra_newskb
without the lock to decide whether first_skb is still owned:

if (first_skb && first_iplen && !defer && first_skb != xtfs->ra_newskb)

Between spin_unlock and this read, a concurrent CPU running
iptfs_reassem_cont() (or the drop_timer hrtimer) can complete
reassembly, NULL xtfs->ra_newskb, and free the skb. The check then
evaluates first_skb != NULL as true, and pskb_trim/ip_summed/consume_skb
operate on the freed skb — a use-after-free in skbuff_head_cache.

Replace the unlocked read with a local bool that records whether
first_skb was handed to the reassembly state in the current call. The
flag is set after the existing spin_unlock, before the break, using the
pointer equality that is stable at that point (first_skb == skb iff
first_skb was stored in ra_newskb).

AI Analysis

Use-after-free vulnerability in the Linux kernel's xfrm: iptfs module

Basic Information

ID CVE-2026-53240

Source Linux

Published Jun 25, 2026 at 08:39

Modified Jun 28, 2026 at 06:40

Affected Product

Vendor Linux

Product Linux

Version 3f3339885fb343b7b42d7c34717108ce07da24ae

Affected Versions Linux Linux 3f3339885fb343b7b42d7c34717108ce07da24ae
Linux Linux 3f3339885fb343b7b42d7c34717108ce07da24ae
Linux Linux 3f3339885fb343b7b42d7c34717108ce07da24ae
Linux Linux 6.14

AI Assessment

AI Score 8.8 / 10

AI Severity High

Vendor Linux

Product Linux Kernel

Version 3f3339885fb343b7b42d7c34717108ce07da24ae, 6.14

References

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: iptfs: fix use-after-free on first_skb in __input_process_payload\n\n__input_process_payload() stores first_skb into xtfs->ra_newskb under\ndrop_lock when starting partial reassembly, then unlocks and breaks out\nof the processing loop. The post-loop check reads xtfs->ra_newskb\nwithout the lock to decide whether first_skb is still owned:\n\n    if (first_skb && first_iplen && !defer && first_skb != xtfs->ra_newskb)\n\nBetween spin_unlock and this read, a concurrent CPU running\niptfs_reassem_cont() (or the drop_timer hrtimer) can complete\nreassembly, NULL xtfs->ra_newskb, and free the skb. The check then\nevaluates first_skb != NULL as true, and pskb_trim/ip_summed/consume_skb\noperate on the freed skb \u2014 a use-after-free in skbuff_head_cache.\n\nReplace the unlocked read with a local bool that records whether\nfirst_skb was handed to the reassembly state in the current call. The\nflag is set after the existing spin_unlock, before the break, using the\npointer equality that is stable at that point (first_skb == skb iff\nfirst_skb was stored in ra_newskb).",
    "published": "2026-06-25T08:39:35.809Z",
    "modified": "2026-06-28T06:40:48.086Z",
    "type": "cve",
    "title": "xfrm: iptfs: fix use-after-free on first_skb in __input_process_payload",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/8d9a79fbf5172d9c4c0146057af2360913265a11\nhttps://git.kernel.org/stable/c/ff2ee35b6ce5fa8a8e24ea50b15733d5c8780198\nhttps://git.kernel.org/stable/c/eb48730bb827d1550401a5d391903f9d90b493c8",
    "id": "CVE-2026-53240",
    "bulletinFamily": "",
    "cwe": null,
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    "sourceData": "Linux Linux 3f3339885fb343b7b42d7c34717108ce07da24ae\nLinux Linux 3f3339885fb343b7b42d7c34717108ce07da24ae\nLinux Linux 3f3339885fb343b7b42d7c34717108ce07da24ae\nLinux Linux 6.14",
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    "product": "Linux",
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    "ai_description": "Use-after-free vulnerability in the Linux kernel's xfrm: iptfs module",
    "ai_severity": "High",
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