{"id":"CVE-2026-98570","summary":"net: ipv6: keep room for the mac header in dst_dev_overhead()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: keep room for the mac header in dst_dev_overhead()\n\nThe seg6, ioam6 and rpl lwtunnels size their skb_cow_head() request as\nthe length they are about to push plus dst_dev_overhead(), then push the\nnew headers and rebuild the mac header below them with\nskb_mac_header_rebuild().  That rebuild needs skb-\u003emac_len of headroom,\nbut dst_dev_overhead() leaves LL_RESERVED_SPACE() of the egress device,\n16 bytes for plain Ethernet.\n\nWhere the mac header is longer than that, as it is on ingress through a\nVLAN device with reorder_hdr off, the rebuild runs out of room:\nskb_set_mac_header(skb, -skb-\u003emac_len) computes a negative offset,\nstores it unchecked in the u16 skb-\u003emac_header, and the memmove that\nfollows writes skb-\u003emac_len bytes about 64 KB past skb-\u003ehead.\nForwarding plain ping6 traffic through such a device reproduces it on\nall five seg6 encapsulation modes and on the rpl and ioam6 inline paths;\nskb-\u003emac_header comes back as 65534 on a 704-byte head.\n\nReturn the larger of the two.  The helper already returns skb-\u003emac_len\nwhen it has no dst, so this only makes the other branch agree, and it\ncovers every caller rather than each call site in turn.","modified":"2026-10-20T02:30:33.188981828Z","published":"2026-10-18T15:18:36.308Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98570.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/36c07127924f11fc5741a780abcaaf808fe9ef13"},{"type":"WEB","url":"https://git.kernel.org/stable/c/87cd6b717e4069dca34e0866e57eaeb44d3b173e"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98570.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98570"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"dce525185bc92864e5a318040285ee070563fe34"},{"fixed":"36c07127924f11fc5741a780abcaaf808fe9ef13"},{"fixed":"87cd6b717e4069dca34e0866e57eaeb44d3b173e"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.12.16"},{"fixed":"6.13"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.13.4"},{"fixed":"6.14"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.15.179"},{"fixed":"5.16"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.1.130"},{"fixed":"6.2"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6.6.81"},{"fixed":"6.7"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5.10.235"},{"fixed":"5.11"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8471e228448a818e4c27cab4b681b2e758e46cf5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c432cd18a07b623651ed15ea167bd303467004cc"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"634710a372ba65bee667c2f6e58a97658c639eab"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c447c5a9c47bb4858ab12bf90879fe595d2b7f46"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"ab9de9c48316d2622d3bf353916b99971570e2c9"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2fcc9f3798ef82399564d247458e69abd10e683b"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"371d8dc298b4f59e99b4564ac5d906fce0932c69"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"b26f015dfb07b6be12d005a0ed0c5c43b7bedbf3"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c0b11dc50590e10590b39dcda79835cd32f49d00"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4c12c3c8abd8b888945d31e7bdbb0d8b73032fc5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"25d8e065c7972dc98fd7a4cac322d5367eaede88"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4a855c5aec41bf84922224ab7a74e088776e3ac4"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"a9f0407414e16176fdbbbd298c9e18d6dfdf96bc"}]}],"versions":["v6.12.113","v6.12.112","v6.12.111","v6.12.110","v6.12.109","v6.12.108","v6.12.107","v6.12.106","v6.12.105","v6.12.104","v6.12.103","v6.12.102","v6.12.101","v6.12.100","v6.12.99","v6.12.98","v6.12.97","v6.12.96","v6.12.95","v6.12.94","v6.12.93","v6.12.92","v6.12.91","v6.12.90","v6.12.89","v6.12.88","v6.12.87","v6.12.86","v6.12.85","v6.12.84","v6.12.83","v6.12.82","v6.12.81","v6.12.80","v6.12.79","v6.12.78","v6.12.77","v6.12.76","v6.12.75","v6.12.74","v6.12.73","v6.12.72","v6.12.71","v6.12.70","v6.12.69","v6.12.68","v6.12.67","v6.12.66","v6.12.65","v6.12.64","v6.12.63","v6.12.62","v6.12.61","v6.12.60","v6.12.59","v6.12.58","v6.12.57","v6.12.56","v6.12.55","v6.12.54","v6.12.53","v6.12.52","v6.12.51","v6.12.50","v6.12.49","v6.12.48","v6.12.47","v6.12.46","v6.12.45","v6.12.44","v6.12.43","v6.12.42","v6.12.41","v6.12.40","v6.12.39","v6.12.38","v6.12.37","v6.12.36","v6.12.35","v6.12.34","v6.12.33","v6.12.32","v6.12.31","v6.12.30","v6.12.29","v6.12.28","v6.12.27","v6.12.26","v6.12.25","v6.12.24","v6.12.23","v6.12.22","v6.12.21","v6.12.20","v6.12.19","v6.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