# CVE-2026-3407: YosysHQ yosys BLIF File rtlil.h set heap-based overflow

> A heap-based buffer overflow in the Yosys BLIF parser allows local attackers to execute arbitrary code or cause a denial of service.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Mar 2026
- **Updated:** 2 Mar 2026
- **Also known as:** GHSA-vc6w-j78g-3gch

## What is CVE-2026-3407?

CVE-2026-3407 is a medium-severity memory corruption vulnerability in YosysHQ yosys, published on 2 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability was determined in YosysHQ yosys up to 0.62. This affects the function Yosys::RTLIL::Const::set of the file kernel/rtlil.h of the component BLIF File Parser. This manipulation causes heap-based buffer overflow. It is possible to launch the attack on the local host. The exploit has been publicly disclosed and may be utilized. Applying a patch is the recommended action to fix this issue. It appears that the issue is not reproducible all the time.

Weakness: CWE-122 (Heap-based Buffer Overflow), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-3407?


## How do I fix CVE-2026-3407?

No fix has been published for CVE-2026-3407 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3407 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3407 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3407 and fix it if it is affected.

What it is: CVE-2026-3407 is a medium-severity memory corruption vulnerability in YosysHQ yosys, published on 2 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3407 exists.

Affected product: YosysHQ yosys. 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-2026-3407/ (Markdown: https://insights.sbomify.com/CVE-2026-3407/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3407
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3407
- OSV: https://osv.dev/vulnerability/CVE-2026-3407

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-3407/
Summaries are generated and may contain mistakes; the official description above is the record.