{"id":"CVE-2026-98239","state":"PUBLISHED","title":"net: lan743x: fix RX checksum use-after-free","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: lan743x: fix RX checksum use-after-free\n\nlan743x_rx_process_buffer() adds each non-first receive buffer to the\nhead skb's frag_list.  On the last descriptor, lan743x_rx_trim_skb()\nlinearizes the head and frees the fragment skb metadata.\n\nThe checksum-success path then writes ip_summed through the local skb\npointer, which still points to the final fragment.  This causes a\nuse-after-free write when a packet spans more than one receive buffer.\n\nSet ip_summed on the surviving head skb instead.  Multi-buffer receive\ncan occur after a live MTU increase because existing ring entries keep\ntheir old buffer size until they are replenished.\n\nA KUnit test invoking lan743x_rx_process_buffer() with a two-buffer\npacket produced a one-byte KASAN use-after-free write before this change.\nThe same test passed after the change.  The driver object also builds\nwith W=1.  This was not tested on physical LAN743x hardware.","publishedAt":"2026-10-06T08:45:10.611Z","updatedAt":"2026-10-19T09:16:10.911Z","severity":{"score":8.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"0e52886c4324c9897c2c62f92be3dc8316cee67e","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"a58024835c704419bb46d2a34e5223f65605f958","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"6fe5c3a2503983abb431d93faeadfc7f5e6a7e33","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"5c216bfa9fb7b36804485e67975e9c98055b31ef","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"161a403c8625e152de03d1da22bbf9cda6dc9f9f","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"a9ce4053dc945c5372dedba5017ee675b30dc0c5","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/ethernet/microchip/lan743x_main.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.112","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.54","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.8","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/ethernet/microchip/lan743x_main.c"]}],"references":["https://git.kernel.org/stable/c/0e52886c4324c9897c2c62f92be3dc8316cee67e","https://git.kernel.org/stable/c/a58024835c704419bb46d2a34e5223f65605f958","https://git.kernel.org/stable/c/6fe5c3a2503983abb431d93faeadfc7f5e6a7e33","https://git.kernel.org/stable/c/5c216bfa9fb7b36804485e67975e9c98055b31ef","https://git.kernel.org/stable/c/161a403c8625e152de03d1da22bbf9cda6dc9f9f","https://git.kernel.org/stable/c/a9ce4053dc945c5372dedba5017ee675b30dc0c5"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98239.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98239","state":"PUBLISHED","datePublished":"2026-10-06T08:45:10.611Z","dateUpdated":"2026-10-19T09:16:10.911Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.329Z"},"containers":{"cna":{"title":"net: lan743x: fix RX checksum use-after-free","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: lan743x: fix RX checksum use-after-free\n\nlan743x_rx_process_buffer() adds each non-first receive buffer to the\nhead skb's frag_list.  On the last descriptor, lan743x_rx_trim_skb()\nlinearizes the head and frees the fragment skb metadata.\n\nThe checksum-success path then writes ip_summed through the local skb\npointer, which still points to the final fragment.  This causes a\nuse-after-free write when a packet spans more than one receive buffer.\n\nSet ip_summed on the surviving head skb instead.  Multi-buffer receive\ncan occur after a live MTU increase because existing ring entries keep\ntheir old buffer size until they are replenished.\n\nA KUnit test invoking lan743x_rx_process_buffer() with a two-buffer\npacket produced a one-byte KASAN use-after-free write before this change.\nThe same test passed after the change.  The driver object also builds\nwith W=1.  This was not tested on physical LAN743x hardware."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"0e52886c4324c9897c2c62f92be3dc8316cee67e","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"a58024835c704419bb46d2a34e5223f65605f958","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"6fe5c3a2503983abb431d93faeadfc7f5e6a7e33","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"5c216bfa9fb7b36804485e67975e9c98055b31ef","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"161a403c8625e152de03d1da22bbf9cda6dc9f9f","versionType":"git"},{"version":"cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a","status":"affected","lessThan":"a9ce4053dc945c5372dedba5017ee675b30dc0c5","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/ethernet/microchip/lan743x_main.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.112","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.54","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.8","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/ethernet/microchip/lan743x_main.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/0e52886c4324c9897c2c62f92be3dc8316cee67e"},{"url":"https://git.kernel.org/stable/c/a58024835c704419bb46d2a34e5223f65605f958"},{"url":"https://git.kernel.org/stable/c/6fe5c3a2503983abb431d93faeadfc7f5e6a7e33"},{"url":"https://git.kernel.org/stable/c/5c216bfa9fb7b36804485e67975e9c98055b31ef"},{"url":"https://git.kernel.org/stable/c/161a403c8625e152de03d1da22bbf9cda6dc9f9f"},{"url":"https://git.kernel.org/stable/c/a9ce4053dc945c5372dedba5017ee675b30dc0c5"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The UAF write runs in lan743x_rx_process_buffer() (NAPI RX) while it handles an ordinary received Ethernet/IP frame from a remote sender. The sender's frame must be larger than the pre-change buffer size so the chip spreads it across several ring descriptors, which a routed jumbo-MTU path can deliver.\nAC:H - Buffers are sized mtu+ETH_HLEN+FCS+2 and the MAC caps frames at mtu+18 (MAC_RX_FSE_), so multi-buffer frames only occur after an admin raises the MTU on a live interface, while stale ring entries remain, or through the chip's occasional extra-buffer quirk. The remote attacker cannot produce either condition.\nPR:N - The trigger is a received frame with a valid checksum handled in the NAPI poll path, lan743x_rx_napi_poll -> lan743x_rx_process_buffer. The sender needs no authentication or credentials on the host.\nUI:N - Once the ring holds stale smaller buffers, no user on the victim needs to do anything; sending the oversized frame triggers the stale write. The admin's MTU change is already counted in AC:H.\nS:U - The freed sk_buff and the corrupted slab memory are inside the kernel itself; no VM, IOMMU or sandbox boundary is crossed.\nC:H - After skb_linearize() in lan743x_rx_trim_skb() frees the frag_list skb, its skbuff_head_cache slot can be reused by another skb. The stale write then hits a live object the attacker can steer with packet timing, which counts as a use-after-free per the scoring guidance.\nI:H - skb->ip_summed = CHECKSUM_UNNECESSARY is written into a freed sk_buff. If the slot has been reallocated, this corrupts another live skb and can make the stack accept forged or corrupted packets without checking their checksums. It is heap memory corruption.\nA:H - Writing into a freed and possibly reused sk_buff from the RX softirq can corrupt slab state and oops or panic the kernel; KASAN flagged the write in the author's KUnit reproducer."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:16:10.911Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.12.112"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.18.54"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.2.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}