CVE-2026-98442: net/sched: act_ct: fix helper UAF due to extensions realloc
In the Linux kernel, the following vulnerability has been resolved:
net/sched: actct: fix helper UAF due to extensions realloc
While calling the helpers, a raw pointer to the extensions area is wired into expectations list:
-> nfcthelper() -> helper->help() -> nfctexpectrelatedreport() -> nfctexpectinsert() -> hlistaddheadrcu(&exp->lnode, &masterhelp->expectations)
In case the connection is not confirmed yet, more extensions can be added afterwards with extadd() 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
Upgrade
ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
Upgrade
ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
Upgrade
ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
Upgrade
ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
Upgrade
ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Upgrade
Upgrade
azurelinux/kernelto a version that resolves this vulnerability.Fixed in 6.6.161.1-1
Event History
Frequently Asked Questions
What conditions are required for this use-after-free to occur?
The affected path requires conntrack helpers to be called for a connection that has not yet been confirmed, followed by additional extension additions that reallocate the connection's extension storage. The stale extension pointer can then later be accessed when an expectation is removed.
How can I determine whether a kernel build contains the fix?
Check whether the kernel source or vendor backport includes the fix represented by the referenced stable commits: 1679bbf5fbeac52a310b1a58b2b301bbf388bdbf, 812c16a255e7773a544e88b39ae6daed25544d30, or 8988f4d11f3fba0ab38122178836c683ad516a05. The fix changes helper invocation ordering so helpers run only after other extensions have been added.