# CVE-2026-71855: Suricata flow: IPv4/IPv6 hash collision can reuse wrong flow state

> Attackers can bypass Suricata detection by causing IPv4/IPv6 flow hash collisions, leading to incorrect flow state reuse and missed threats.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 25 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-71855, GHSA-fvwh-wjcq-2586, UBUNTU-CVE-2026-71855

## What is CVE-2026-71855?

CVE-2026-71855 is a medium-severity vulnerability in Oisf Suricata, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Suricata is a network Intrusion Detection System, Intrusion Prevention System and Network Security Monitoring engine. Prior to 7.0.17 and 8.0.6, src/flow-hash.c can treat an IPv4 and IPv6 flow as equal without comparing the IP family when their raw address words, ports, protocol, VLAN, recursion level, live device, and hash bucket align. An IPv6 packet can therefore reuse IPv4 flow state or the reverse, causing incorrect flowbit state, detection bypass, or IP-only bypass. This issue is fixed in versions 8.0.6 and 7.0.17.

Weakness: CWE-697 (Incorrect Comparison)

## Which versions are affected by CVE-2026-71855?

It affects 1 product.


Products: Oisf Suricata.

## How do I fix CVE-2026-71855?

Upgrade to a fixed version.

## Is CVE-2026-71855 being exploited?

There is no known exploitation of CVE-2026-71855 in the wild and no public exploit code.

## Other vulnerabilities in Oisf Suricata

- [CVE-2023-35853](https://insights.sbomify.com/CVE-2023-35853/): Code injection in n/a (critical 9.8)
- [CVE-2021-37592](https://insights.sbomify.com/CVE-2021-37592/): Other in n/a (critical 9.8)
- [CVE-2018-10244](https://insights.sbomify.com/CVE-2018-10244/): Integer overflow in n/a (critical 9.8)
- [CVE-2026-94083](https://insights.sbomify.com/CVE-2026-94083/): Memory corruption in Suricata (critical 9.4)
- [CVE-2026-94084](https://insights.sbomify.com/CVE-2026-94084/): Use after free in Suricata (critical 9.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-71855 and fix it if it is affected.

What it is: CVE-2026-71855 is a medium-severity vulnerability in Oisf Suricata, published on 18 Sep 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-2026-71855 in the wild and no public exploit code.

Affected product: Oisf Suricata. 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-2026-71855/ (Markdown: https://insights.sbomify.com/CVE-2026-71855/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-71855
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-71855
- OSV: https://osv.dev/vulnerability/CVE-2026-71855

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-71855/
Summaries are generated and may contain mistakes; the official description above is the record.