{"id":"CVE-2026-72020","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-72020","summary":"ipvs: reset full ip_vs_seq structs in ip_vs_conn_new","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nipvs: reset full ip_vs_seq structs in ip_vs_conn_new\n\nCommit 9a05475cebdd (\"ipvs: avoid kmem_cache_zalloc in\nip_vs_conn_new\") changed ip_vs_conn_new() to allocate an ip_vs_conn\nobject with kmem_cache_alloc().  The function then initializes many\nfields explicitly, but only resets in_seq.delta and out_seq.delta in the\ntwo struct ip_vs_seq members.\n\nThat leaves init_seq and previous_delta uninitialized.  This is normally\nharmless while the corresponding IP_VS_CONN_F_IN_SEQ or\nIP_VS_CONN_F_OUT_SEQ flag is clear.  For connections learned from a sync\nmessage, however, ip_vs_proc_conn() preserves those flags from\nIP_VS_CONN_F_BACKUP_MASK and passes opt=NULL when the message omits\nIPVS_OPT_SEQ_DATA.  In that case the new connection can be hashed with\nSEQ flags set but with the rest of in_seq/out_seq still containing stale\nslab data.\n\nWhen a packet for such a connection is later handled by an IPVS\napplication helper, vs_fix_seq() and vs_fix_ack_seq() use\nprevious_delta and init_seq to rewrite TCP sequence numbers.  A malformed\nsync message can therefore make forwarded packets carry stale slab bytes\nin their TCP seq/ack numbers, and can also corrupt the forwarded TCP\nflow.\n\nReset both struct ip_vs_seq members completely before publishing the\nconnection.  This matches the existing \"reset struct ip_vs_seq\" comment\nand keeps the sequence-adjustment gates inactive unless valid sequence\ndata is installed later.","published":"2026-08-15T05:51:46.675Z","modified":"2026-08-18T03:56:18.195566977Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"5.10.261"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2975324d164c552b028632f107b567302863b7f6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/32c299e28b8eea6cbbd23b97dc61401e9ef9c445"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3bf9a260188b2a5449cbddc032a749ab433fe328"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6335ab62d5fc9ed875279238233fba3462c168f5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6378c5cb360eb1750f88839d7c3613ea92ac1816"},{"type":"WEB","url":"https://git.kernel.org/stable/c/83fb4c2c5344f02eac929f66de3c9d1adfcde04c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9e36602cbec552286f7e691cfd366525c565ee74"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d0eed7177e822cab83141e5c44b2aa345c7fd379"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72020.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72020"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T03:56:18.195566977Z"}}