# CVE-2021-27935: Information disclosure in n/a

> Attackers can offline brute-force passwords by extracting password hashes from user cookies, leading to account takeover.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 3 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-75vm-hh32-424x

## What is CVE-2021-27935?

CVE-2021-27935 is a high-severity vulnerability in n/a, published on 3 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in AdGuard before 0.105.2. An attacker able to get the user's cookie is able to bruteforce their password offline, because the hash of the password is stored in the cookie.

Weakness: CWE-522 (Insufficiently Protected Credentials)

## Which versions are affected by CVE-2021-27935?

It affects 1 product.


Products: Adguard Adguard Home.

## How do I fix CVE-2021-27935?

No fix has been published for CVE-2021-27935 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27935 being exploited?

There is no known exploitation of CVE-2021-27935 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27935 and fix it if it is affected.

What it is: CVE-2021-27935 is a high-severity vulnerability in n/a, published on 3 Mar 2021. 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-2021-27935 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-2021-27935/ (Markdown: https://insights.sbomify.com/CVE-2021-27935/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27935
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27935
- OSV: https://osv.dev/vulnerability/CVE-2021-27935

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27935/
Summaries are generated and may contain mistakes; the official description above is the record.