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VulnerabilityPublished Updated

CVE-2026-72020: Linux kernel · ipvs: reset full ip_vs_seq structs in ip_vs_conn_new

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in d0eed7177e822cab83141e5c44b2aa345c7fd379 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 12:55 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.7% chance of exploitation in 30 days – higher than 53% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in d0eed7177e822cab83141e5c44b2aa345c7fd379, 2975324d164c552b028632f107b567302863b7f6, 6378c5cb360eb1750f88839d7c3613ea92ac1816 +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 9a05475cebdd6341884b5901e53870be26e65158, < d0eed7177e822cab83141e5c44b2aa345c7fd379
Fixed in
  • d0eed7177e822cab83141e5c44b2aa345c7fd379
LinuxLinuxAffected
  • ≥ 9a05475cebdd6341884b5901e53870be26e65158, < 2975324d164c552b028632f107b567302863b7f6
Fixed in
  • 2975324d164c552b028632f107b567302863b7f6
LinuxLinuxAffected
  • ≥ 9a05475cebdd6341884b5901e53870be26e65158, < 6378c5cb360eb1750f88839d7c3613ea92ac1816
Fixed in
  • 6378c5cb360eb1750f88839d7c3613ea92ac1816
LinuxLinuxAffected
  • ≥ 9a05475cebdd6341884b5901e53870be26e65158, < 6335ab62d5fc9ed875279238233fba3462c168f5
Fixed in
  • 6335ab62d5fc9ed875279238233fba3462c168f5
LinuxLinuxAffected
  • ≥ 9a05475cebdd6341884b5901e53870be26e65158, < 83fb4c2c5344f02eac929f66de3c9d1adfcde04c
Fixed in
  • 83fb4c2c5344f02eac929f66de3c9d1adfcde04c
LinuxLinuxAffected
  • ≥ 9a05475cebdd6341884b5901e53870be26e65158, < 32c299e28b8eea6cbbd23b97dc61401e9ef9c445
Fixed in
  • 32c299e28b8eea6cbbd23b97dc61401e9ef9c445

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.

References

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