{"id":"CVE-2026-68296","summary":"net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: gre: fix lltx regression for GRE tunnels with SEQ/CSUM\n\nBefore commit 00d066a4d4ed (\"netdev_features: convert NETIF_F_LLTX to\ndev-\u003elltx\"), NETIF_F_LLTX was set unconditionally in both\n__gre_tunnel_init() and ip6gre_tnl_init_features() alongside\nGRE_FEATURES:\n\n    dev-\u003efeatures |= GRE_FEATURES | NETIF_F_LLTX;\n\nWhen that commit converted NETIF_F_LLTX to the dev-\u003elltx flag, it\nplaced 'dev-\u003elltx = true' after the SEQ/CSUM early returns instead\nof before them. This causes GRE/GRETAP/ip6gre tunnels with SEQ or\nCSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition\naround their ndo_start_xmit. Since GRE xmit re-enters the stack via\nip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the\nunderlay device.\n\n  CPU0                        CPU1\n  ----                        ----\n  lock(&qdisc_xmit_lock_key#6);\n                              lock(&qdisc_xmit_lock_key#3);\n                              lock(&qdisc_xmit_lock_key#6);\n  lock(&qdisc_xmit_lock_key#3);\n\nFix by moving dev-\u003elltx = true before the early returns in both\nfunctions, restoring the original unconditional behavior.","modified":"2026-08-12T04:18:47.495601716Z","published":"2026-08-10T12:02:29.464Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68296.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2bffe379023512d280337c70faeb6a8cc435db5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/675ed582c1aa4d919dd535490de08c015005c653"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9f948e9aede9678f4103457daf2bc9dd54c65a06"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68296.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68296"},{"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":"00d066a4d4edbe559ba6c35153da71d4b2b8a383"},{"fixed":"9f948e9aede9678f4103457daf2bc9dd54c65a06"},{"fixed":"15a1c5f2ed2eeb3daad8d5766fd506aeda4710f3"},{"fixed":"2bffe379023512d280337c70faeb6a8cc435db5e"},{"fixed":"675ed582c1aa4d919dd535490de08c015005c653"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68296.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.12.0"},{"fixed":"6.12.101"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.42"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68296.json"}}],"schema_version":"1.9.0"}