# CVE-2026-74569: netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp()

> An integer overflow in the Linux kernel's SIP connection tracking allows out-of-bounds reads, potentially causing crashes or information leaks.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-96003, BELL-CVE-2026-74569, DEBIAN-CVE-2026-74569, GHSA-jjgj-x6vq-56wx, UBUNTU-CVE-2026-74569

## What is CVE-2026-74569?

CVE-2026-74569 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp()

sip_help_tcp() stores the size change of each NAT-rewritten SIP message
in s16 diff and accumulates it in s16 tdiff, but a single message can
grow by more than S16_MAX while the packet stays under the 65535
enlarge_skb() limit: nf_nat_sip() rewrites every matching URI, and a long
Contact list expands the message by tens of kilobytes. diff then wraps,
and "datalen = datalen + diff - msglen" yields a huge unsigned datalen,
so the next iteration's ct_sip_get_header() reads past the linearized skb
tail.

Widen diff, tdiff and the seq_adjust hook to s32. Both are bounded by the
65535 byte packet limit, and the seqadj core is already s32
(nf_ct_seqadj_set() takes s32), so no previously accepted input is
rejected.

  BUG: KASAN: use-after-free in ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464)
  Read of size 1 at addr ffff888010800000 by task ksoftirqd/1/25
   ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464)
   sip_help_tcp (net/netfilter/nf_conntrack_sip.c:1694)
   nf_confirm (net/netfilter/nf_conntrack_proto.c:183)
   nf_hook_slow (net/netfilter/core.c:619)
   ip6_output (net/ipv6/ip6_output.c:246)
   ip6_forward (net/ipv6/ip6_output.c:690)
   ipv6_rcv (net/ipv6/ip6_input.c:351)
   __netif_receive_skb_one_core (net/core/dev.c:6212)
   process_backlog (net/core/dev.c:6676)
   __napi_poll (net/core/dev.c:7735)
   net_rx_action (net/core/dev.c:7955)
   handle_softirqs (kernel/softirq.c:622)
   run_ksoftirqd (kernel/softirq.c:1076)
   ...

## Which versions are affected by CVE-2026-74569?


## How do I fix CVE-2026-74569?

Apply the vendor's patch.

## Is CVE-2026-74569 being exploited?

There is no known exploitation of CVE-2026-74569 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74569 and fix it if it is affected.

What it is: CVE-2026-74569 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74569 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-2026-74569/ (Markdown: https://insights.sbomify.com/CVE-2026-74569/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74569
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74569
- OSV: https://osv.dev/vulnerability/CVE-2026-74569

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74569/
Summaries are generated and may contain mistakes; the official description above is the record.