# CVE-2026-34873: An issue was discovered in Mbed TLS 3.5.0 through 4.0.0.


- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 1 Apr 2026
- **Updated:** 2 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-34873, ECHO-fc34-8f29-f217, GHSA-q24g-gcpv-7264, ROOT-OS-DEBIAN-12-CVE-2026-34873, UBUNTU-CVE-2026-34873

## What is CVE-2026-34873?

CVE-2026-34873 is a critical vulnerability in n/a, published on 1 Apr 2026. 

### Official description

An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-34873?

It affects 1 product.


Products: Trustedfirmware Mbed Tls.

## How do I fix CVE-2026-34873?

Upgrade to a fixed version.

## Is CVE-2026-34873 being exploited?

There is no known exploitation of CVE-2026-34873 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2026-34875](https://insights.sbomify.com/CVE-2026-34875/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-49195](https://insights.sbomify.com/CVE-2024-49195/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-45158](https://insights.sbomify.com/CVE-2024-45158/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-45159](https://insights.sbomify.com/CVE-2024-45159/): Auth bypass in n/a (critical 9.8)
- [CVE-2023-45199](https://insights.sbomify.com/CVE-2023-45199/): Mbed TLS 3.2.x through 3.4.x before 3.5 has a Buffer Overflow that can lead to remote Code execution. (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34873 and fix it if it is affected.

What it is: CVE-2026-34873 is a critical vulnerability in n/a, published on 1 Apr 2026. 
Exploitation: There is no known exploitation of CVE-2026-34873 in the wild and no public exploit code.

Affected product: n/a. 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-2026-34873/ (Markdown: https://insights.sbomify.com/CVE-2026-34873/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34873
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34873
- OSV: https://osv.dev/vulnerability/CVE-2026-34873

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34873/
Summaries are generated and may contain mistakes; the official description above is the record.