{"id":"CVE-2026-98372","summary":"xfrm: iptfs: fix stack OOB read in iptfs_skb_reset_frag_walk()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: iptfs: fix stack OOB read in iptfs_skb_reset_frag_walk()\n\niptfs_skb_reset_frag_walk() advances to the fragment containing @offset\nwith an unbounded loop:\n\n\twhile (offset \u003e= walk-\u003epast + walk-\u003efrags[walk-\u003efragi].len)\n\t\twalk-\u003epast += walk-\u003efrags[walk-\u003efragi++].len;\n\nwalk-\u003efragi is advanced and walk-\u003efrags[walk-\u003efragi] is dereferenced\nwithout ever checking fragi against walk-\u003enr_frags. When the requested\noffset is at or beyond the total length spanned by the walk's fragments,\nfragi runs past nr_frags and off the end of the fixed-size on-stack\nfrags[MAX_SKB_FRAGS + 1] array, reading out-of-bounds stack memory.\n\nThe two callers behave differently: iptfs_skb_add_frags() already guards\nagainst this with\n\n\tif (!walk-\u003enr_frags ||\n\t    offset \u003e= walk-\u003etotal + walk-\u003einitial_offset)\n\t\treturn len;\n\nbut iptfs_skb_can_add_frags() has no such guard and calls\niptfs_skb_reset_frag_walk() unconditionally, so it performs the\nout-of-range walk. Its own \"fragi \u003c walk-\u003enr_frags\" bound check runs only\nafterwards, too late to prevent the read.\n\nThis is reachable from the receive path: a crafted IP-TFS (AGGFRAG)\npayload delivered to an IPTFS SA drives iptfs_reassem_cont() -\u003e\niptfs_skb_can_add_frags() with an offset past the fragment total, e.g.:\n\n  BUG: KASAN: stack-out-of-bounds in iptfs_skb_reset_frag_walk+0x235/0x250\n  Read of size 4 at addr ffff888008ad7210 by task repro/345\n   iptfs_skb_reset_frag_walk+0x235/0x250 net/xfrm/xfrm_iptfs.c:392\n   iptfs_skb_can_add_frags+0x155/0x310  net/xfrm/xfrm_iptfs.c:420\n   iptfs_reassem_cont+0xcf8/0x1140      net/xfrm/xfrm_iptfs.c:902\n   iptfs_input_ordered+0x552/0x670      net/xfrm/xfrm_iptfs.c:1280\n   iptfs_input+0x3d6/0xde0              net/xfrm/xfrm_iptfs.c:1741\n   xfrm_input+0x282f/0x6140             net/xfrm/xfrm_input.c:700\n   xfrm4_esp_rcv+0x93/0x120             net/ipv4/xfrm4_protocol.c:104\n   ip_rcv+0x278/0x2d0                   net/ipv4/ip_input.c:612\n\nGive iptfs_skb_can_add_frags() the same up-front guard that\niptfs_skb_add_frags() already has, so the walk is never entered with an\nout-of-range offset. When it triggers, the caller falls back to the\nexisting linearize-and-copy path, which is safe.","modified":"2026-10-08T02:52:58.552305057Z","published":"2026-10-06T08:46:56.529Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98372.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/7e1c6884a0b494b7e3f204877f94c1e07a117bf7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d042487dc118e494db2e2c1382310255c90ff544"},{"type":"WEB","url":"https://git.kernel.org/stable/c/da56d0ee93d1bad779b0486f2fab92d1bc1f0cf3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98372.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98372"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5f2b6a9095743a6bf1f34c43c4fe78fa8bdf5ad7"},{"fixed":"7e1c6884a0b494b7e3f204877f94c1e07a117bf7"},{"fixed":"da56d0ee93d1bad779b0486f2fab92d1bc1f0cf3"},{"fixed":"d042487dc118e494db2e2c1382310255c90ff544"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98372.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.18.54"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98372.json"}}],"schema_version":"1.9.0"}