Critical severity · published Aug 15, 2026
CVE-2026-72020
ipvs: reset full ip_vs_seq structs in ip_vs_conn_new
9.8
CVSS
0.7%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 53% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
Linux · Linux
9a05475cebdd6341884b5901e53870be26e65158 before 3bf9a260188b2a5449cbddc032a749ab433fe328; 9a05475cebdd6341884b5901e53870be26e65158 before 6378c5cb360eb1750f88839d7c3613ea92ac1816; 9a05475cebdd6341884b5901e53870be26e65158 before 32c299e28b8eea6cbbd23b97dc61401e9ef9c445; 9a05475cebdd6341884b5901e53870be26e65158 before 9e36602cbec552286f7e691cfd366525c565ee74; 9a05475cebdd6341884b5901e53870be26e65158 before d0eed7177e822cab83141e5c44b2aa345c7fd379; 9a05475cebdd6341884b5901e53870be26e65158 before 83fb4c2c5344f02eac929f66de3c9d1adfcde04c; +3 more · source: vendor