# CVE-2020-26236: Verification Code Hijacking in ScratchVerifier

> An attacker can hijack the verification process to log into another user's account by racing to complete the login after the victim submits the code.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **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:** No
- **Published:** 20 Nov 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-99cr-hvf7-85g9

## What is CVE-2020-26236?

CVE-2020-26236 is a high-severity vulnerability in ScratchVerifier, published on 20 Nov 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

In ScratchVerifier before commit a603769, an attacker can hijack the verification process to log into someone else's account on any site that uses ScratchVerifier for logins. A possible exploitation would follow these steps: 1. User starts login process. 2. Attacker attempts login for user, and is given the same verification code. 3. User comments code as part of their normal login. 4. Before user can, attacker completes the login process now that the code is commented. 5. User gets a failed login and attacker now has control of the account. Since commit a603769 starting a login twice will generate different verification codes, causing both user and attacker login to fail. For clients that rely on a clone of ScratchVerifier not hosted by the developers, their users may attempt to finish the login process as soon as possible after commenting the code. There is no reliable way for the attacker to know before the user can finish the process that the user has commented the code, so this vulnerability only really affects those who comment the code and then take several seconds before finishing the login.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2020-26236?

It affects 1 product.


Products: Scratchverifier Scratchverifier.

## How do I fix CVE-2020-26236?

No fix has been published for CVE-2020-26236 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-26236 being exploited?

There is no known exploitation of CVE-2020-26236 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-26236 and fix it if it is affected.

What it is: CVE-2020-26236 is a high-severity vulnerability in ScratchVerifier, published on 20 Nov 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-2020-26236 in the wild and no public exploit code.

Affected product: ScratchVerifier. 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-2020-26236/ (Markdown: https://insights.sbomify.com/CVE-2020-26236/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26236
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26236
- OSV: https://osv.dev/vulnerability/CVE-2020-26236

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-26236/
Summaries are generated and may contain mistakes; the official description above is the record.