# CVE-2026-74492: netfilter: ipset: do not update comments from kernel-side hash adds

> A race condition in Linux kernel ipset allows attackers to trigger a use-after-free via concurrent packet-side adds and table resizes, potentially leading to code execution or crashes.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-96521, BELL-CVE-2026-74492, DEBIAN-CVE-2026-74492, GHSA-j8fq-xqcv-34c2, UBUNTU-CVE-2026-74492

## What is CVE-2026-74492?

CVE-2026-74492 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

netfilter: ipset: do not update comments from kernel-side hash adds

mtype_resize() copies comment pointers with memcpy(), not the comment
objects themselves. During the window after an entry has been copied but
before the table swap and backlog replay, the old table is still
published for packet-side updates while the replacement-table entry
already holds the same ip_set_comment_rcu pointer.

If xt_SET --add-set ... --exist hits that old entry in this window,
mtype_add() calls ip_set_init_comment() even though packet-side adds
carry no comment payload. That call frees the shared comment through the
old entry, so the replacement-table entry now holds a stale pointer.
When the queued add is replayed on the new table, mtype_add() calls
ip_set_init_comment() again and strlen() dereferences the stale pointer.

Fix this in mtype_add() by skipping ip_set_init_comment() when
ext->target marks a packet-side add. Userspace adds still update
comments, while packet-side adds can no longer free comment storage
shared with a resize copy.

## Which versions are affected by CVE-2026-74492?


## How do I fix CVE-2026-74492?

Apply the vendor's patch.

## Is CVE-2026-74492 being exploited?

There is no known exploitation of CVE-2026-74492 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74492 and fix it if it is affected.

What it is: CVE-2026-74492 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74492 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74492/ (Markdown: https://insights.sbomify.com/CVE-2026-74492/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74492
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74492
- OSV: https://osv.dev/vulnerability/CVE-2026-74492

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74492/
Summaries are generated and may contain mistakes; the official description above is the record.