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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ip_tunnel: prevent perpetual headroom growth\n\nsyzkaller triggered following kasan splat:\nBUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\nRead of size 1 at addr ffff88812fb4000e by task syz-executor183/5191\n[..]\n kasan_report+0xda/0x110 mm/kasan/report.c:588\n __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\n skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]\n ___skb_get_hash net/core/flow_dissector.c:1791 [inline]\n __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856\n skb_get_hash include/linux/skbuff.h:1556 [inline]\n ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748\n ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\n xmit_one net/core/dev.c:3548 [inline]\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349\n dev_queue_xmit include/linux/netdevice.h:3134 [inline]\n neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592\n ...\n ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235\n ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323\n ..\n iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82\n ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831\n ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\n xmit_one net/core/dev.c:3548 [inline]\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\n ...\n\nThe splat occurs because skb-\u003edata points past skb-\u003ehead allocated area.\nThis is because neigh layer does:\n  __skb_pull(skb, skb_network_offset(skb));\n\n... but skb_network_offset() returns a negative offset and __skb_pull()\narg is unsigned.  IOW, we skb-\u003edata gets \"adjusted\" by a huge value.\n\nThe negative value is returned because skb-\u003ehead and skb-\u003edata distance is\nmore than 64k and skb-\u003enetwork_header (u16) has wrapped around.\n\nThe bug is in the ip_tunnel infrastructure, which can cause\ndev-\u003eneeded_headroom to increment ad infinitum.\n\nThe syzkaller reproducer consists of packets getting routed via a gre\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\ntunnel.  The ipip encapsulation finds gre0 as next output device.\n\nThis results in the following pattern:\n\n1). First packet is to be sent out via gre0.\nRoute lookup found an output device, ipip0.\n\n2).\nip_tunnel_xmit for gre0 bumps gre0-\u003eneeded_headroom based on the future\noutput device, rt.dev-\u003eneeded_headroom (ipip0).\n\n3).\nip output / start_xmit moves skb on to ipip0. which runs the same\ncode path again (xmit recursion).\n\n4).\nRouting step for the post-gre0-encap packet finds gre0 as output device\nto use for ipip0 encapsulated packet.\n\ntunl0-\u003eneeded_headroom is then incremented based on the (already bumped)\ngre0 device headroom.\n\nThis repeats for every future packet:\n\ngre0-\u003eneeded_headroom gets inflated because previous packets\u0027 ipip0 step\nincremented rt-\u003edev (gre0) headroom, and ipip0 incremented because gre0\nneeded_headroom was increased.\n\nFor each subsequent packet, gre/ipip0-\u003eneeded_headroom grows until\npost-expand-head reallocations result in a skb-\u003ehead/data distance of\nmore than 64k.\n\nOnce that happens, skb-\u003enetwork_header (u16) wraps around when\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\nafter the headroom expansion/reallocation.\n\nAfter this skb_network_offset(skb) returns a different (and negative)\nresult post headroom expansion.\n\nThe next trip to neigh layer (or anything else that would __skb_pull the\nnetwork header) makes skb-\u003edata point to a memory location outside\nskb-\u003ehead area.\n\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\nprevent perpetual increase instead of dropping the headroom increment\ncompletely."
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            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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              "value": "AV:L - The attacker must locally configure a two-device ip_tunnel routing cycle (gre0 \u2194 tunl0) via rtnetlink/ioctl and then transmit packets through a local socket; a remote peer cannot create the tunnel topology that drives the headroom growth.\nAC:L - The headroom inflation is fully deterministic \u2014 each transmitted packet monotonically increases dev-\u003eneeded_headroom until the u16 network_header wraps, with no race and no dependence on memory layout the attacker cannot influence. The required ipip/gre modules are standard on virtually all distributions.\nPR:L - An unprivileged user gains CAP_NET_ADMIN over a private netns via unshare -Urn, since rtnetlink checks netlink_net_capable() against the netns owning user_ns, and tunl0/gre0 fallback devices are auto-created in every netns because sysctl_fb_tunnels_only_for_init_net defaults to 0.\nUI:N - The attacker performs the entire setup and packet transmission alone; no victim action or interaction is required.\nS:U - The corruption occurs in kernel memory within the same security authority; no VM, IOMMU, or hypervisor boundary is crossed.\nC:H - After the offset overflow skb-\u003edata points ~4GB away in the kernel direct map, producing the syzbot-confirmed KASAN out-of-bounds/use-after-free read in __skb_flow_dissect, and the resulting packet\u0027s payload is read from that arbitrary kernel memory and transmitted to the attacker-chosen tunnel destination \u2014 up to ~64KB of kernel memory disclosure.\nI:H - skb_push() only validates data \u003c head, so iptunnel_xmit() writes a 20-byte IP header (with attacker-controlled saddr/daddr/tos/ttl) plus the GRE header and attacker-chosen GRE key into out-of-bounds kernel memory, giving a partially controlled write primitive suitable for corrupting adjacent kernel objects.\nA:H - The confirmed use-after-free/out-of-bounds access reliably causes a KASAN report, oops, or panic (unmapped-address dereference or skb_under_panic), and the unbounded needed_headroom growth also forces ever-larger skb reallocations."
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    "nvd": "{\"cve\":{\"id\":\"CVE-2024-26804\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-04-04T09:15:09.217\",\"lastModified\":\"2026-08-12T18:17:17.730\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: ip_tunnel: prevent perpetual headroom growth\\n\\nsyzkaller triggered following kasan splat:\\nBUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\\nRead of size 1 at addr ffff88812fb4000e by task syz-executor183/5191\\n[..]\\n kasan_report+0xda/0x110 mm/kasan/report.c:588\\n __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\\n skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]\\n ___skb_get_hash net/core/flow_dissector.c:1791 [inline]\\n __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856\\n skb_get_hash include/linux/skbuff.h:1556 [inline]\\n ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748\\n ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308\\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\\n xmit_one net/core/dev.c:3548 [inline]\\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\\n __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349\\n dev_queue_xmit include/linux/netdevice.h:3134 [inline]\\n neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592\\n ...\\n ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235\\n ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323\\n ..\\n iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82\\n ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831\\n ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665\\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\\n xmit_one net/core/dev.c:3548 [inline]\\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\\n ...\\n\\nThe splat occurs because skb-\u003edata points past skb-\u003ehead allocated area.\\nThis is because neigh layer does:\\n  __skb_pull(skb, skb_network_offset(skb));\\n\\n... but skb_network_offset() returns a negative offset and __skb_pull()\\narg is unsigned.  IOW, we skb-\u003edata gets \\\"adjusted\\\" by a huge value.\\n\\nThe negative value is returned because skb-\u003ehead and skb-\u003edata distance is\\nmore than 64k and skb-\u003enetwork_header (u16) has wrapped around.\\n\\nThe bug is in the ip_tunnel infrastructure, which can cause\\ndev-\u003eneeded_headroom to increment ad infinitum.\\n\\nThe syzkaller reproducer consists of packets getting routed via a gre\\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\\ntunnel.  The ipip encapsulation finds gre0 as next output device.\\n\\nThis results in the following pattern:\\n\\n1). First packet is to be sent out via gre0.\\nRoute lookup found an output device, ipip0.\\n\\n2).\\nip_tunnel_xmit for gre0 bumps gre0-\u003eneeded_headroom based on the future\\noutput device, rt.dev-\u003eneeded_headroom (ipip0).\\n\\n3).\\nip output / start_xmit moves skb on to ipip0. which runs the same\\ncode path again (xmit recursion).\\n\\n4).\\nRouting step for the post-gre0-encap packet finds gre0 as output device\\nto use for ipip0 encapsulated packet.\\n\\ntunl0-\u003eneeded_headroom is then incremented based on the (already bumped)\\ngre0 device headroom.\\n\\nThis repeats for every future packet:\\n\\ngre0-\u003eneeded_headroom gets inflated because previous packets\u0027 ipip0 step\\nincremented rt-\u003edev (gre0) headroom, and ipip0 incremented because gre0\\nneeded_headroom was increased.\\n\\nFor each subsequent packet, gre/ipip0-\u003eneeded_headroom grows until\\npost-expand-head reallocations result in a skb-\u003ehead/data distance of\\nmore than 64k.\\n\\nOnce that happens, skb-\u003enetwork_header (u16) wraps around when\\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\\nafter the headroom expansion/reallocation.\\n\\nAfter this skb_network_offset(skb) returns a different (and negative)\\nresult post headroom expansion.\\n\\nThe next trip to neigh layer (or anything else that would __skb_pull the\\nnetwork header) makes skb-\u003edata point to a memory location outside\\nskb-\u003ehead area.\\n\\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\\nprevent perpetual increase instead of dropping the headroom increment\\ncompletely.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: ip_tunnel: evita el crecimiento perpetuo del espacio libre syzkaller activado despu\u00e9s de kasan splat: ERROR: KASAN: use-after-free en __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 Lectura del tama\u00f1o 1 en la direcci\u00f3n ffff88812fb4000e mediante la tarea syz-executor183/5191 [..] kasan_report+0xda/0x110 mm/kasan/report.c:588 __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170 skb_flow_dissect_flow_key incluir/linux /skbuff.h:1514 [en l\u00ednea] ___skb_get_hash net/core/flow_dissector.c:1791 [en l\u00ednea] __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856 skb_get_hash include/linux/skbuff.h:1556 [en l\u00ednea] ip_tunnel_xmit +0x1855/0x33c0 net/ipv4/ip_tunnel.c:748 ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308 __netdev_start_xmit include/linux/netdevice.h:4940 [en l\u00ednea] netdev_start_xmit include/linux/netdevice.h:4954 [en l\u00ednea] xmit_one net/core/dev.c:3548 [en l\u00ednea] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349 dev_queue_xmit include/linux/netdevice .h:3134 [en l\u00ednea] neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592 ... ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235 ip_finish_output+0x31/0x310 net/ipv4/ip_output.c :323 .. iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831 ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665 __netdev_start_xmit incluir /linux /netdevice.h:4940 [en l\u00ednea] netdev_start_xmit include/linux/netdevice.h:4954 [en l\u00ednea] xmit_one net/core/dev.c:3548 [en l\u00ednea] dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564 . .. El s\u00edmbolo se produce porque skb-\u0026gt;data apunta m\u00e1s all\u00e1 del \u00e1rea asignada de skb-\u0026gt;head. Esto se debe a que la capa vecina hace: __skb_pull(skb, skb_network_offset(skb)); ... pero skb_network_offset() devuelve un desplazamiento negativo y el argumento __skb_pull() no est\u00e1 firmado. OIA, nosotros, skb-\u0026gt;los datos, se \\\"ajustan\\\" en un valor enorme. El valor negativo se devuelve porque la distancia de skb-\u0026gt;head y skb-\u0026gt;data es superior a 64k y skb-\u0026gt;network_header (u16) se ha ajustado. El error est\u00e1 en la infraestructura ip_tunnel, lo que puede hacer que dev-\u0026gt;needed_headroom se incremente hasta el infinito. El reproductor syzkaller consta de paquetes que se enrutan a trav\u00e9s de un t\u00fanel gre y una ruta de paquetes encapsulados gre que apuntan a otro t\u00fanel (ipip). La encapsulaci\u00f3n ipip encuentra gre0 como el siguiente dispositivo de salida. Esto da como resultado el siguiente patr\u00f3n: 1). El primer paquete se enviar\u00e1 a trav\u00e9s de gre0. La b\u00fasqueda de ruta encontr\u00f3 un dispositivo de salida, ipip0. 2). ip_tunnel_xmit para gre0 aumenta gre0-\u0026gt;needed_headroom seg\u00fan el dispositivo de salida futuro, rt.dev-\u0026gt;needed_headroom (ipip0). 3). ipoutput/start_xmit mueve skb a ipip0. que ejecuta la misma ruta de c\u00f3digo nuevamente (xmit recursividad). 4). El paso de enrutamiento para el paquete post-gre0-encap encuentra gre0 como dispositivo de salida para usar con el paquete encapsulado ipip0. tunl0-\u0026gt;needed_headroom luego se incrementa seg\u00fan el espacio libre del dispositivo gre0 (ya aumentado). Esto se repite para cada paquete futuro: gre0-\u0026gt;needed_headroom se infla porque el paso ipip0 de los paquetes anteriores increment\u00f3 el espacio libre rt-\u0026gt;dev (gre0), y ipip0 se increment\u00f3 porque se aument\u00f3 el espacio necesario_headroom de gre0. Para cada paquete posterior, gre/ipip0-\u0026gt;needed_headroom crece hasta que las reasignaciones posteriores a la expansi\u00f3n del cabezal dan como resultado una distancia skb-\u0026gt;head/data de m\u00e1s de 64k. Una vez que eso sucede, skb-\u0026gt;network_header (u16) se ajusta cuando pskb_expand_head intenta asegurarse de que skb_network_offset() no cambie despu\u00e9s de la expansi\u00f3n/reasignaci\u00f3n del espacio libre. Despu\u00e9s de esto, skb_network_offset(skb) devuelve un resultado diferente (y negativo) posterior a la expansi\u00f3n del espacio libre.---trucado---\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/ipv4/ip_tunnel.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"f81e94d2dcd2397137edcb8b85f4c5bed5d22383\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"2e95350fe9db9d53c701075060ac8ac883b68aee\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"afec0c5cd2ed71ca95a8b36a5e6d03333bf34282\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"ab63de24ebea36fe73ac7121738595d704b66d96\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"049d7989c67e8dd50f07a2096dbafdb41331fb9b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"243aad830e8a4cdda261626fbaeddde16b08d04a\",\"lessThan\":\"5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"03017375b0122453e6dda833ff7bd4191915def5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"2.6.33.2\",\"lessThan\":\"2.6.34\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/ipv4/ip_tunnel.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"2.6.34\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"2.6.34\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.4.271\",\"lessThanOrEqual\":\"5.4.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.212\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.151\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.81\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.21\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.7.9\",\"lessThanOrEqual\":\"6.7.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.8\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-08-12T17:39:19.030766Z\",\"id\":\"CVE-2024-26804\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-416\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"2.6.34\",\"versionEndExcluding\":\"5.4.271\",\"matchCriteriaId\":\"04A5E4E0-8C32-4FCD-9A72-B0AF07EA991E\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.5\",\"versionEndExcluding\":\"5.10.212\",\"matchCriteriaId\":\"01B34738-A022-44A9-9250-DCBC76539CB9\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.11\",\"versionEndExcluding\":\"5.15.151\",\"matchCriteriaId\":\"EEAFD33E-C22F-4FB1-A417-9C96AB3E0358\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"6.1.81\",\"matchCriteriaId\":\"EC825B0E-DFCA-4034-9B92-F111A4E2A732\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.2\",\"versionEndExcluding\":\"6.6.21\",\"matchCriteriaId\":\"B19074A2-9FE5-4E7D-9E2D-020F95013ADA\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.7\",\"versionEndExcluding\":\"6.7.9\",\"matchCriteriaId\":\"1C538467-EDA0-4A9A-82EB-2925DE9FF827\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.8:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"B9F4EA73-0894-400F-A490-3A397AB7A517\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.8:rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"056BD938-0A27-4569-B391-30578B309EE3\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.8:rc3:*:*:*:*:*:*\",\"matchCriteriaId\":\"F02056A5-B362-4370-9FF8-6F0BD384D520\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.8:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"62075ACE-B2A0-4B16-829D-B3DA5AE5CC41\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.8:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"A780F817-2A77-4130-A9B7-5C25606314E3\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.8:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"AEB9199B-AB8F-4877-8964-E2BA95B5F15C\"}]}]},{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"07B237A9-69A3-4A9C-9DA0-4E06BD37AE73\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\"]},{\"url\":\"https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-18T14:14:31+00:00",
      "cve": "CVE-2024-26804",
      "id": "CVE-2024-26804",
      "initial_release_date": "2024-04-04T00:00:00+00:00",
      "product_status:fixed": "929",
      "product_status:known_affected": "64",
      "product_status:known_not_affected": "9",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: ip_tunnel: prevent perpetual headroom growth",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2024/cve-2024-26804.json",
      "version": "3"
    },
    "vulnrichment": {
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The required ipip/gre modules are standard on virtually all distributions.\\nPR:L - An unprivileged user gains CAP_NET_ADMIN over a private netns via unshare -Urn, since rtnetlink checks netlink_net_capable() against the netns owning user_ns, and tunl0/gre0 fallback devices are auto-created in every netns because sysctl_fb_tunnels_only_for_init_net defaults to 0.\\nUI:N - The attacker performs the entire setup and packet transmission alone; no victim action or interaction is required.\\nS:U - The corruption occurs in kernel memory within the same security authority; no VM, IOMMU, or hypervisor boundary is crossed.\\nC:H - After the offset overflow skb-\u003edata points ~4GB away in the kernel direct map, producing the syzbot-confirmed KASAN out-of-bounds/use-after-free read in __skb_flow_dissect, and the resulting packet\u0027s payload is read from that arbitrary kernel memory and transmitted to the attacker-chosen tunnel destination \\u2014 up to ~64KB of kernel memory disclosure.\\nI:H - skb_push() only validates data \u003c head, so iptunnel_xmit() writes a 20-byte IP header (with attacker-controlled saddr/daddr/tos/ttl) plus the GRE header and attacker-chosen GRE key into out-of-bounds kernel memory, giving a partially controlled write primitive suitable for corrupting adjacent kernel objects.\\nA:H - The confirmed use-after-free/out-of-bounds access reliably causes a KASAN report, oops, or panic (unmapped-address dereference or skb_under_panic), and the unbounded needed_headroom growth also forces ever-larger skb reallocations.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"243aad830e8a4cdda261626fbaeddde16b08d04a\", \"lessThan\": \"f81e94d2dcd2397137edcb8b85f4c5bed5d22383\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"243aad830e8a4cdda261626fbaeddde16b08d04a\", 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\"03017375b0122453e6dda833ff7bd4191915def5\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"2.6.33.2\", \"lessThan\": \"2.6.34\", \"versionType\": \"semver\"}], \"programFiles\": [\"net/ipv4/ip_tunnel.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.6.34\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"2.6.34\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.4.271\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.212\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.151\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.81\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.21\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.7.9\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.7.*\"}, {\"status\": \"unaffected\", \"version\": \"6.8\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/ipv4/ip_tunnel.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/f81e94d2dcd2397137edcb8b85f4c5bed5d22383\"}, {\"url\": \"https://git.kernel.org/stable/c/2e95350fe9db9d53c701075060ac8ac883b68aee\"}, {\"url\": \"https://git.kernel.org/stable/c/afec0c5cd2ed71ca95a8b36a5e6d03333bf34282\"}, {\"url\": \"https://git.kernel.org/stable/c/ab63de24ebea36fe73ac7121738595d704b66d96\"}, {\"url\": \"https://git.kernel.org/stable/c/a0a1db40b23e8ff86dea2786c5ea1470bb23ecb9\"}, {\"url\": \"https://git.kernel.org/stable/c/049d7989c67e8dd50f07a2096dbafdb41331fb9b\"}, {\"url\": \"https://git.kernel.org/stable/c/5ae1e9922bbdbaeb9cfbe91085ab75927488ac0f\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: ip_tunnel: prevent perpetual headroom growth\\n\\nsyzkaller triggered following kasan splat:\\nBUG: KASAN: use-after-free in __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\\nRead of size 1 at addr ffff88812fb4000e by task syz-executor183/5191\\n[..]\\n kasan_report+0xda/0x110 mm/kasan/report.c:588\\n __skb_flow_dissect+0x19d1/0x7a50 net/core/flow_dissector.c:1170\\n skb_flow_dissect_flow_keys include/linux/skbuff.h:1514 [inline]\\n ___skb_get_hash net/core/flow_dissector.c:1791 [inline]\\n __skb_get_hash+0xc7/0x540 net/core/flow_dissector.c:1856\\n skb_get_hash include/linux/skbuff.h:1556 [inline]\\n ip_tunnel_xmit+0x1855/0x33c0 net/ipv4/ip_tunnel.c:748\\n ipip_tunnel_xmit+0x3cc/0x4e0 net/ipv4/ipip.c:308\\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\\n xmit_one net/core/dev.c:3548 [inline]\\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\\n __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4349\\n dev_queue_xmit include/linux/netdevice.h:3134 [inline]\\n neigh_connected_output+0x42c/0x5d0 net/core/neighbour.c:1592\\n ...\\n ip_finish_output2+0x833/0x2550 net/ipv4/ip_output.c:235\\n ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323\\n ..\\n iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82\\n ip_tunnel_xmit+0x1dbc/0x33c0 net/ipv4/ip_tunnel.c:831\\n ipgre_xmit+0x4a1/0x980 net/ipv4/ip_gre.c:665\\n __netdev_start_xmit include/linux/netdevice.h:4940 [inline]\\n netdev_start_xmit include/linux/netdevice.h:4954 [inline]\\n xmit_one net/core/dev.c:3548 [inline]\\n dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3564\\n ...\\n\\nThe splat occurs because skb-\u003edata points past skb-\u003ehead allocated area.\\nThis is because neigh layer does:\\n  __skb_pull(skb, skb_network_offset(skb));\\n\\n... but skb_network_offset() returns a negative offset and __skb_pull()\\narg is unsigned.  IOW, we skb-\u003edata gets \\\"adjusted\\\" by a huge value.\\n\\nThe negative value is returned because skb-\u003ehead and skb-\u003edata distance is\\nmore than 64k and skb-\u003enetwork_header (u16) has wrapped around.\\n\\nThe bug is in the ip_tunnel infrastructure, which can cause\\ndev-\u003eneeded_headroom to increment ad infinitum.\\n\\nThe syzkaller reproducer consists of packets getting routed via a gre\\ntunnel, and route of gre encapsulated packets pointing at another (ipip)\\ntunnel.  The ipip encapsulation finds gre0 as next output device.\\n\\nThis results in the following pattern:\\n\\n1). First packet is to be sent out via gre0.\\nRoute lookup found an output device, ipip0.\\n\\n2).\\nip_tunnel_xmit for gre0 bumps gre0-\u003eneeded_headroom based on the future\\noutput device, rt.dev-\u003eneeded_headroom (ipip0).\\n\\n3).\\nip output / start_xmit moves skb on to ipip0. which runs the same\\ncode path again (xmit recursion).\\n\\n4).\\nRouting step for the post-gre0-encap packet finds gre0 as output device\\nto use for ipip0 encapsulated packet.\\n\\ntunl0-\u003eneeded_headroom is then incremented based on the (already bumped)\\ngre0 device headroom.\\n\\nThis repeats for every future packet:\\n\\ngre0-\u003eneeded_headroom gets inflated because previous packets\u0027 ipip0 step\\nincremented rt-\u003edev (gre0) headroom, and ipip0 incremented because gre0\\nneeded_headroom was increased.\\n\\nFor each subsequent packet, gre/ipip0-\u003eneeded_headroom grows until\\npost-expand-head reallocations result in a skb-\u003ehead/data distance of\\nmore than 64k.\\n\\nOnce that happens, skb-\u003enetwork_header (u16) wraps around when\\npskb_expand_head tries to make sure that skb_network_offset() is unchanged\\nafter the headroom expansion/reallocation.\\n\\nAfter this skb_network_offset(skb) returns a different (and negative)\\nresult post headroom expansion.\\n\\nThe next trip to neigh layer (or anything else that would __skb_pull the\\nnetwork header) makes skb-\u003edata point to a memory location outside\\nskb-\u003ehead area.\\n\\nv2: Cap the needed_headroom update to an arbitarily chosen upperlimit to\\nprevent perpetual increase instead of dropping the headroom increment\\ncompletely.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.271\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.212\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.151\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.81\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.21\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.7.9\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.8\", \"versionStartIncluding\": \"2.6.34\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"2.6.33.2\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T11:27:24.842Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2024-26804\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-12T17:39:59.942Z\", \"dateReserved\": \"2024-02-19T14:20:24.179Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-04-04T08:20:31.305Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
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}