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CVE-2026-98442

Linux: net/sched: act_ct: fix helper UAF due to extensions realloc

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.17%Chance of exploitation activity in the next 30 days, higher than 5% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in31f5fe29a572037ee19c233dfe506849940c484bAlso 1679bbf5fbeac52a310b1a58b2b301bbf388bdbf, 812c16a255e7773a544e88b39ae6daed25544d30 and 1 moreCVE List
Published18 Oct 2026Updated 21 Oct 2026CVE List

What fixes it

  • 31f5fe29a572037ee19c233dfe506849940c484bLinuxCVE List
  • 1679bbf5fbeac52a310b1a58b2b301bbf388bdbfLinuxCVE List
  • 812c16a255e7773a544e88b39ae6daed25544d30LinuxCVE List
  • 8988f4d11f3fba0ab38122178836c683ad516a05LinuxCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_ct: fix helper UAF due to extensions realloc

While calling the helpers, a raw pointer to the extensions area is wired into expectations list:

-> nf_ct_helper() -> helper->help() -> nf_ct_expect_related_report() -> nf_ct_expect_insert() -> hlist_add_head_rcu(&exp->lnode, &master_help->expectations)

In case the connection is not confirmed yet, more extensions can be added afterwards with *_ext_add() calls reallocating the extension space and leaving the now invalid pointer in the expectations list that is later accessed while removing the expectation.

Make sure that helpers are called at the end after all the other extensions are already added.

Note that the helper rejection now leaves the mark and labels set, but that's not different from how the NAT was handled before or how the mark and the labels were handled on confirmation failure. And there are no atomicity guarantees provided by the API anyway.

Text from CVE List

Affected versions 12

  • Linuxaffected: a21b06e7319129994f339ed47f512bbe57b77f5b before 31f5fe29a572037ee19c233dfe506849940c484bCVE List
  • Linuxaffected: a21b06e7319129994f339ed47f512bbe57b77f5b before 1679bbf5fbeac52a310b1a58b2b301bbf388bdbfCVE List
  • Linuxaffected: a21b06e7319129994f339ed47f512bbe57b77f5b before 812c16a255e7773a544e88b39ae6daed25544d30CVE List
  • Linuxaffected: a21b06e7319129994f339ed47f512bbe57b77f5b before 8988f4d11f3fba0ab38122178836c683ad516a05CVE List
  • Linuxaffected: a21b06e7319129994f339ed47f512bbe57b77f5b before dad19b59da050cb60d3f7023dac2a042a84bf0bdCVE List
  • Linuxaffected: 6.2CVE List
  • Linuxunaffected: all versions before 6.2CVE List
  • Linuxunaffected: 6.6.160 through 6.6.*CVE List
  • Linuxunaffected: 6.12.112 through 6.12.*CVE List
  • Linuxunaffected: 6.18.55 through 6.18.*CVE List
  • Linuxunaffected: 7.2.9 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 5