# CVE-2026-5500: Improper Validation of AES-GCM Authentication Tag Length in PKCS#7 Envelope Allows Authentication Bypass

> A man-in-the-middle can bypass PKCS#7 authentication by truncating the AES-GCM tag, allowing forged data acceptance in wolfSSL.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Apr 2026
- **Updated:** 10 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-5500, GHSA-m77r-vqw2-hffx, JLSEC-2026-729, UBUNTU-CVE-2026-5500

## What is CVE-2026-5500?

CVE-2026-5500 is a high-severity vulnerability in Wolfssl Wolfssl, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

wolfSSL's wc_PKCS7_DecodeAuthEnvelopedData() does not properly sanitize the AES-GCM authentication tag length received and has no lower bounds check. A man-in-the-middle can therefore truncate the mac field from 16 bytes to 1 byte, reducing the tag check from 2⁻¹²⁸ to 2⁻⁸.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-5500?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-5500?

Apply the vendor's patch.

## Is CVE-2026-5500 being exploited?

There is no known exploitation of CVE-2026-5500 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-2026-5500 and fix it if it is affected.

What it is: CVE-2026-5500 is a high-severity vulnerability in Wolfssl Wolfssl, published on 10 Apr 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-2026-5500 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-2026-5500/ (Markdown: https://insights.sbomify.com/CVE-2026-5500/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5500
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5500
- OSV: https://osv.dev/vulnerability/CVE-2026-5500

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5500/
Summaries are generated and may contain mistakes; the official description above is the record.