CVE-2026-72020

In the Linux kernel, the following vulnerability has been resolved:

ipvs: reset full ip_vs_seq structs in ip_vs_conn_new

Commit 9a05475cebdd (ipvs: avoid kmem_cache_zalloc in ip_vs_conn_new) changed ip_vs_conn_new() to allocate an ip_vs_conn object with kmem_cache_alloc(). The function then initializes many fields explicitly, but only resets in_seq.delta and out_seq.delta in the two struct ip_vs_seq members.

That leaves init_seq and previous_delta uninitialized. This is normally harmless while the corresponding IP_VS_CONN_F_IN_SEQ or IP_VS_CONN_F_OUT_SEQ flag is clear. For connections learned from a sync message, however, ip_vs_proc_conn() preserves those flags from IP_VS_CONN_F_BACKUP_MASK and passes opt=NULL when the message omits IPVS_OPT_SEQ_DATA. In that case the new connection can be hashed with SEQ flags set but with the rest of in_seq/out_seq still containing stale slab data.

When a packet for such a connection is later handled by an IPVS application helper, vs_fix_seq() and vs_fix_ack_seq() use previous_delta and init_seq to rewrite TCP sequence numbers. A malformed sync message can therefore make forwarded packets carry stale slab bytes in their TCP seq/ack numbers, and can also corrupt the forwarded TCP flow.

Reset both struct ip_vs_seq members completely before publishing the connection. This matches the existing reset struct ip_vs_seq comment and keeps the sequence-adjustment gates inactive unless valid sequence data is installed later.

Affected Software

References

• https://git.kernel.org/stable/c/2975324d164c552b028632f107b567302863b7f6
• https://git.kernel.org/stable/c/32c299e28b8eea6cbbd23b97dc61401e9ef9c445
• https://git.kernel.org/stable/c/3bf9a260188b2a5449cbddc032a749ab433fe328
• https://git.kernel.org/stable/c/6335ab62d5fc9ed875279238233fba3462c168f5
• https://git.kernel.org/stable/c/6378c5cb360eb1750f88839d7c3613ea92ac1816
• https://git.kernel.org/stable/c/83fb4c2c5344f02eac929f66de3c9d1adfcde04c
• https://git.kernel.org/stable/c/9e36602cbec552286f7e691cfd366525c565ee74
• https://git.kernel.org/stable/c/d0eed7177e822cab83141e5c44b2aa345c7fd379