CyberSecBulletin
CVE-2026-72021NVD status: Received

In the Linux kernel, the following vulnerability has been resolved: ipvs: use parsed transport…

Published Updated By the CyberSecBulletin desk

CVE-2026-72021 is a high-severity improper input validation vulnerability in Linux, with a CVSS 3.1 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions d2b8b1557ec07ea1bb5dddbceaf4dfe63d388e27, 9f94573ab962a9e81954b755da016fa3cd2f5039, 290e9e8389b556efc603522e28bd1543846aa336 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.59% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to d2b8b1557ec07ea1bb5dddbceaf4dfe63d388e27 or 9f94573ab962a9e81954b755da016fa3cd2f5039 or 290e9e8389b556efc603522e28bd1543846aa336 or 9cb5ac594ca76d3a71803b23b74c835b0721e628, whichever matches your release line, or a later version.
  2. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, d2b8b1557ec07ea1bb5dddbceaf4dfe63d388e27; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, 9f94573ab962a9e81954b755da016fa3cd2f5039; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, 290e9e8389b556efc603522e28bd1543846aa336; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, 9cb5ac594ca76d3a71803b23b74c835b0721e628; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, a4a2d2e483d79cc2ad3a170674cf159644acf22b; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, 247d055504dcc852e539b9f7f30d19f9741474bf; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, e5d0bb8871668f20de8f3c94b5ae3f372346bc6e; 2906f66a5682e5670a5eefe991843689b8d8563f up to, but not including, 2f75c0faa3361b28e36cc0512b3299e163e25789; and 1 more rangesd2b8b1557ec07ea1bb5dddbceaf4dfe63d388e27, 9f94573ab962a9e81954b755da016fa3cd2f5039, 290e9e8389b556efc603522e28bd1543846aa336, 9cb5ac594ca76d3a71803b23b74c835b0721e628, a4a2d2e483d79cc2ad3a170674cf159644acf22b, 247d055504dcc852e539b9f7f30d19f9741474bf

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
LowLimited modification of data is possible.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: ipvs: use parsed transport offset in SCTP state lookup set_sctp_state() reads the SCTP chunk header again in order to drive the IPVS SCTP state table. For IPv6 it computes the offset with sizeof(struct ipv6hdr), while the surrounding IPVS code uses iph.len from ip_vs_fill_iph_skb(), where ipv6_find_hdr() has already skipped extension headers and found the real transport header. This makes the state machine read from the wrong offset for IPv6 SCTP packets that carry extension headers. For example, an INIT packet with an 8-byte destination options header can be scheduled correctly by sctp_conn_schedule(), but set_sctp_state() reads the first byte of the SCTP verification tag as a DATA chunk type. The connection then moves from NONE to ESTABLISHED instead of INIT1, gets the longer established timeout, and updates the active/inactive destination counters incorrectly. This happens even though the SCTP handshake has not completed. Use the parsed transport offset passed down from ip_vs_set_state() for the SCTP chunk-header lookup. For IPv4 and IPv6 packets without extension headers this preserves the existing offset.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Input Validation vulnerabilities

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