# CVE-2026-3549: ECH parsing heap buffer overflow

> An integer underflow in wolfSSL's ECH parsing allows heap buffer overflows, potentially leading to code execution or crashes when ECH is enabled.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Mar 2026
- **Updated:** 24 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-3549, GHSA-j2g5-52p7-mfpc, JLSEC-2026-708, UBUNTU-CVE-2026-3549

## What is CVE-2026-3549?

CVE-2026-3549 is a high-severity memory corruption vulnerability in Wolfssl Wolfssl, published on 19 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Heap Overflow in TLS 1.3 ECH parsing. An integer underflow existed in ECH extension parsing logic when calculating a buffer length, which resulted in writing beyond the bounds of an allocated buffer. Note that in wolfSSL, ECH is off by default, and the ECH standard is still evolving.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-3549?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-3549?

Apply the vendor's patch.

## Is CVE-2026-3549 being exploited?

There is no known exploitation of CVE-2026-3549 in the wild and no public exploit code.

## Other vulnerabilities in Wolfssl Wolfssl

- [CVE-2024-5991](https://insights.sbomify.com/CVE-2024-5991/): Buffer overread in domain name matching (critical 10.0)
- [CVE-2021-37155](https://insights.sbomify.com/CVE-2021-37155/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-36177](https://insights.sbomify.com/CVE-2020-36177/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2896](https://insights.sbomify.com/CVE-2014-2896/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2897](https://insights.sbomify.com/CVE-2014-2897/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3549 and fix it if it is affected.

What it is: CVE-2026-3549 is a high-severity memory corruption vulnerability in Wolfssl Wolfssl, published on 19 Mar 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-2026-3549 in the wild and no public exploit code.

Affected product: Wolfssl Wolfssl. 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-2026-3549/ (Markdown: https://insights.sbomify.com/CVE-2026-3549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3549
- OSV: https://osv.dev/vulnerability/CVE-2026-3549

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3549/
Summaries are generated and may contain mistakes; the official description above is the record.