# CVE-2026-1858: wget2 Improper Certificate Validation

> Attackers can bypass TLS certificate validation in wget2 by reusing certificates with incorrect Key Usage extensions, enabling man-in-the-middle attacks.

- **Severity:** Medium 4.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Apr 2026
- **Updated:** 30 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-1858, GHSA-9h5h-4q77-cphm, UBUNTU-CVE-2026-1858

## What is CVE-2026-1858?

CVE-2026-1858 is a medium-severity vulnerability in gnu wget2, published on 29 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

wget2 accepts a server certificate with incorrect Key Usage (KU) or Extended Key Usage (EKU). If the attackers compromise a certificate (with the associated private key) issued for a different purpose, they may be able to reuse it for TLS server authentication.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-1858?

It affects 1 product.


Products: Gnu Wget2.

## How do I fix CVE-2026-1858?

No fix has been published for CVE-2026-1858 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1858 being exploited?

There is no known exploitation of CVE-2026-1858 in the wild and no public exploit code.

## Other vulnerabilities in gnu wget2

- [CVE-2025-69194](https://insights.sbomify.com/CVE-2025-69194/): Wget2: arbitrary file write via metalink path traversal in gnu wget2 (high 8.8)
- [CVE-2025-69195](https://insights.sbomify.com/CVE-2025-69195/): Wget2: gnu wget2: memory corruption and crash via filename sanitization logic with attacker-controlled urls (high 7.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1858 and fix it if it is affected.

What it is: CVE-2026-1858 is a medium-severity vulnerability in gnu wget2, published on 29 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-2026-1858 in the wild and no public exploit code.

Affected product: gnu wget2. 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-2026-1858/ (Markdown: https://insights.sbomify.com/CVE-2026-1858/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1858
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1858
- OSV: https://osv.dev/vulnerability/CVE-2026-1858

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1858/
Summaries are generated and may contain mistakes; the official description above is the record.