# CVE-2020-26290: Critical security issues in XML encoding in Dex

> Attackers can bypass SAML signature validation in Dex due to XML encoding flaws, allowing unauthorized access if the SAML connector is enabled.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 28 Dec 2020
- **Updated:** 4 Aug 2024
- **Also known as:** openSUSE-SU-2024:10714-1

## What is CVE-2020-26290?

CVE-2020-26290 is a critical vulnerability in dexidp dex, published on 28 Dec 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Dex is a federated OpenID Connect provider written in Go. In Dex before version 2.27.0 there is a critical set of vulnerabilities which impacts users leveraging the SAML connector. The vulnerabilities enables potential signature bypass due to issues with XML encoding in the underlying Go library. The vulnerabilities have been addressed in version 2.27.0 by using the xml-roundtrip-validator from Mattermost (see related references).

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2020-26290?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `dex-oidc` | openSUSE:Tumbleweed | All versions | 2.28.1-1.3 |

Products: Linuxfoundation Dex.

## How do I fix CVE-2020-26290?

Upgrade to a fixed version.

## Is CVE-2020-26290 being exploited?

There is no known exploitation of CVE-2020-26290 in the wild and no public exploit code.

## Other vulnerabilities in dexidp dex

- [CVE-2020-27847](https://insights.sbomify.com/CVE-2020-27847/): Auth bypass in dexidp/dex (critical 9.8)
- [CVE-2022-39222](https://insights.sbomify.com/CVE-2022-39222/): OAuth authorization code exposure in Dex (critical 9.3)
- [CVE-2024-23656](https://insights.sbomify.com/CVE-2024-23656/): Dex 2.37.0 is discarding TLSconfig and always serves deprecated TLS 1.0/1.1 and insecure ciphers (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-26290 and fix it if it is affected.

What it is: CVE-2020-26290 is a critical vulnerability in dexidp dex, published on 28 Dec 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-26290 in the wild and no public exploit code.

Affected product: dexidp dex. 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-2020-26290/ (Markdown: https://insights.sbomify.com/CVE-2020-26290/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26290
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26290
- OSV: https://osv.dev/vulnerability/CVE-2020-26290

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-26290/
Summaries are generated and may contain mistakes; the official description above is the record.