Answer in brief
CVE-2026-90237 records a Unknown severity vulnerability in netfilter: nft_ct: move custom expectation support to helper. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=857b46027d6f91150797295752581b7155b9d0e1 <af3fe52fd108fd38235e4813df62442ed0f1d8ff || >=857b46027d6f91150797295752581b7155b9d0e1 <3679da4ad8be84cddaf40bc307fef1fe13e051ff | af3fe52fd108fd38235e4813df62442ed0f1d8ff, 3679da4ad8be84cddaf40bc307fef1fe13e051ff |
| Linux/Linuxgeneric | 5.3 | Not reported |
Published upstream
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 17, 2026
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 be created at a time given expect_clash() will make nf_ct_expect_related() reports EBUSY. For this reason, relax nf_ct_expect_related() not to drop packets in case expectation creation fails, therefore, expectation creation becomes best effort. To address this issue, add an internal ct helper and attach it to the conntrack entry to streamline the custom ct expectation support with existing ct helpers. Expose a new nf_conntrack_helper_release() function to release the internal helper that is allocated and attached to the conntrack entry to create the custom expectations. The nft_ct module removal always waits for rcu grace period, then the NULL helper callback is observed after this. This patch also restricts the creation of expectations to different helpers other than this custom helper that is created for this type of expectations.
Quoted source text, attributed separately from HOL analysis.