Bug 2516532 (CVE-2026-72020) - CVE-2026-72020 kernel: ipvs: reset full ip_vs_seq structs in ip_vs_conn_new
Summary: CVE-2026-72020 kernel: ipvs: reset full ip_vs_seq structs in ip_vs_conn_new
Keywords:
Status: NEW
Alias: CVE-2026-72020
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-15 06:17 UTC by OSIDB Bzimport
Modified: 2026-08-17 16:10 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
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Description OSIDB Bzimport 2026-08-15 06:17:26 UTC
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.


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