# CVE-2026-55958: Renesas TSIP TLS 1.3 transcript buffer out-of-bounds write in tsip_StoreMessage


- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 25 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-55958, GHSA-8mfx-6cpc-cr47, JLSEC-2026-734, UBUNTU-CVE-2026-55958

## What is CVE-2026-55958?

CVE-2026-55958 is a high-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. 

### Official description

Out-of-bounds write in the Renesas TSIP TLS 1.3 transcript buffer. In tsip_StoreMessage() the capacity check guarding the fixed message bag (MSGBAG_SIZE) sets an error code but fails to return, so execution falls through to an XMEMCPY that writes past the end of the buffer once the accumulated TLS 1.3 handshake transcript exceeds MSGBAG_SIZE (8 KB), corrupting adjacent heap state and potentially causing a remote denial of service crash. The bag is sized to hold a normal handshake, so this is reached only by an unusually large but valid certificate chain, or by a malicious or man-in-the-middle server sending an oversized handshake message to a client that does not strictly verify the chain. This only affects builds using the Renesas TSIP TLS port (WOLFSSL_RENESAS_TSIP_TLS) as a TLS 1.3 client on Renesas MCUs with TSIP hardware enabled, and is rated High within those builds. All other configurations are unaffected.

Weakness: CWE-787 (Out-of-bounds Write), CWE-393 (Return of Wrong Status Code)

## Which versions are affected by CVE-2026-55958?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-55958?

Upgrade to a fixed version.

## Is CVE-2026-55958 being exploited?

There is no known exploitation of CVE-2026-55958 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-2026-55958 and fix it if it is affected.

What it is: CVE-2026-55958 is a high-severity vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. 
Exploitation: There is no known exploitation of CVE-2026-55958 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-2026-55958/ (Markdown: https://insights.sbomify.com/CVE-2026-55958/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55958
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55958
- OSV: https://osv.dev/vulnerability/CVE-2026-55958

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55958/
Summaries are generated and may contain mistakes; the official description above is the record.