{"id":"CVE-2026-98570","title":"net: ipv6: keep room for the mac header in dst_dev_overhead()","summary":"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 …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= dce525185bc92864e5a318040285ee070563fe34 < 36c07127924f11fc5741a780abcaaf808fe9ef13","Linux >= dce525185bc92864e5a318040285ee070563fe34 < 87cd6b717e4069dca34e0866e57eaeb44d3b173e","Linux 8471e228448a818e4c27cab4b681b2e758e46cf5","Linux c432cd18a07b623651ed15ea167bd303467004cc","Linux 634710a372ba65bee667c2f6e58a97658c639eab","Linux c447c5a9c47bb4858ab12bf90879fe595d2b7f46","Linux ab9de9c48316d2622d3bf353916b99971570e2c9","Linux 2fcc9f3798ef82399564d247458e69abd10e683b","Linux 371d8dc298b4f59e99b4564ac5d906fce0932c69","Linux b26f015dfb07b6be12d005a0ed0c5c43b7bedbf3","Linux c0b11dc50590e10590b39dcda79835cd32f49d00","Linux 4c12c3c8abd8b888945d31e7bdbb0d8b73032fc5","Linux 25d8e065c7972dc98fd7a4cac322d5367eaede88","Linux 4a855c5aec41bf84922224ab7a74e088776e3ac4","Linux a9f0407414e16176fdbbbd298c9e18d6dfdf96bc","Linux >= 6.12.16 < 6.13","Linux >= 6.13.4 < 6.14","Linux >= 5.15.179 < 5.16","Linux >= 6.1.130 < 6.2","Linux >= 6.6.81 < 6.7","Linux >= 5.10.235 < 5.11","Linux 6.14"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:18:36.308Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98570","references":[{"url":"https://git.kernel.org/stable/c/36c07127924f11fc5741a780abcaaf808fe9ef13"},{"url":"https://git.kernel.org/stable/c/87cd6b717e4069dca34e0866e57eaeb44d3b173e"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T15:45:12.258Z","slug":"CVE-2026-98570","body":"## Overview\n\nIn 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->mac_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->mac_len) computes a negative offset,\nstores it unchecked in the u16 skb->mac_header, and the memmove that\nfollows writes skb->mac_len bytes about 64 KB past skb->head.\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->mac_header comes back as 65534 on a 704-byte head.\n\nReturn the larger of the two.  The helper already returns skb->mac_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.\n\n## Affected\n\n- `Linux >= dce525185bc92864e5a318040285ee070563fe34 < 36c07127924f11fc5741a780abcaaf808fe9ef13`\n- `Linux >= dce525185bc92864e5a318040285ee070563fe34 < 87cd6b717e4069dca34e0866e57eaeb44d3b173e`\n- `Linux 8471e228448a818e4c27cab4b681b2e758e46cf5`\n- `Linux c432cd18a07b623651ed15ea167bd303467004cc`\n- `Linux 634710a372ba65bee667c2f6e58a97658c639eab`\n- `Linux c447c5a9c47bb4858ab12bf90879fe595d2b7f46`\n- `Linux ab9de9c48316d2622d3bf353916b99971570e2c9`\n- `Linux 2fcc9f3798ef82399564d247458e69abd10e683b`\n- `Linux 371d8dc298b4f59e99b4564ac5d906fce0932c69`\n- `Linux b26f015dfb07b6be12d005a0ed0c5c43b7bedbf3`\n- `Linux c0b11dc50590e10590b39dcda79835cd32f49d00`\n- `Linux 4c12c3c8abd8b888945d31e7bdbb0d8b73032fc5`\n- `Linux 25d8e065c7972dc98fd7a4cac322d5367eaede88`\n- `Linux 4a855c5aec41bf84922224ab7a74e088776e3ac4`\n- `Linux a9f0407414e16176fdbbbd298c9e18d6dfdf96bc`\n- `Linux >= 6.12.16 < 6.13`\n- `Linux >= 6.13.4 < 6.14`\n- `Linux >= 5.15.179 < 5.16`\n- `Linux >= 6.1.130 < 6.2`\n- `Linux >= 6.6.81 < 6.7`\n- `Linux >= 5.10.235 < 5.11`\n- `Linux 6.14`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}