CVE-2026-90237

/// Technical description

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

netfilter: nft_ct: move custom expectation support to helper

Originally, the ct expectation support called nf_ct_helper_ext_add() for

confirmed conntracks, which is invalid, triggering a splat. This was

fixed by commit 1710eb913bdc ("netfilter: nft_ct: skip expectations for

confirmed conntrack") which restricted it to unconfirmed conntracks.

However, early insertion of expectations into the expectations list when

the conntrack is unconfirmed leads to stale entries pointing to the

wrong hlist_head through .pprev due to ct extension reallocation.

Commit 7c9664351980 ("netfilter: move nat hlist_head to nf_conn") moved

the nat hlist_head to nf_conn for this reason:

1. ...

2. When reallocation of extension area occurs we need to fixup the

bysource hash head via hlist_replace_rcu.

I'd rather not increase the size of the struct nf_conn for this feature

has very limited scope: only one expectation can b

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References