CVE-2026-72020: Linux kernel · ipvs: reset full ip_vs_seq structs in ip_vs_conn_new
Affects Linux kernelSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- git.kernel.org/stable/c/3bf9a260188b2a5449cbddc032a749ab433fe328 (opens in a new tab)
- git.kernel.org/stable/c/6378c5cb360eb1750f88839d7c3613ea92ac1816 (opens in a new tab)
- git.kernel.org/stable/c/32c299e28b8eea6cbbd23b97dc61401e9ef9c445 (opens in a new tab)
- git.kernel.org/stable/c/9e36602cbec552286f7e691cfd366525c565ee74 (opens in a new tab)
- git.kernel.org/stable/c/d0eed7177e822cab83141e5c44b2aa345c7fd379 (opens in a new tab)
- git.kernel.org/stable/c/83fb4c2c5344f02eac929f66de3c9d1adfcde04c (opens in a new tab)
- git.kernel.org/stable/c/6335ab62d5fc9ed875279238233fba3462c168f5 (opens in a new tab)
- git.kernel.org/stable/c/2975324d164c552b028632f107b567302863b7f6 (opens in a new tab)