# CVE-2025-13476: Rakuten Viber uses broken or risky cryptographic Algorithm

> Viber Cloak mode uses predictable TLS fingerprints, allowing DPI systems to easily identify and block proxy traffic, undermining censorship circumvention efforts.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** No
- **Published:** 5 Mar 2026
- **Updated:** 6 Mar 2026
- **Also known as:** GHSA-7qg4-wvfj-q8vh

## What is CVE-2025-13476?

CVE-2025-13476 is a critical vulnerability in Rakuten Viber Cloak - Android, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Rakuten Viber Cloak mode in Android v25.7.2.0g and Windows v25.6.0.0–v25.8.1.0 uses a static and predictable TLS ClientHello fingerprint lacking extension diversity, allowing Deep Packet Inspection (DPI) systems to trivially identify and block proxy traffic, undermining censorship circumvention. (CWE-327)

Weakness: CWE-327 (Use of a Broken or Risky Cryptographic Algorithm)

## Which versions are affected by CVE-2025-13476?

It affects 1 product.


Products: Rakuten Viber.

## How do I fix CVE-2025-13476?

No fix has been published for CVE-2025-13476 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-13476 being exploited?

There is no known exploitation of CVE-2025-13476 in the wild and no public exploit code.

## Other vulnerabilities in Rakuten Viber Cloak - Android

- [CVE-2019-18800](https://insights.sbomify.com/CVE-2019-18800/): Information disclosure in n/a (high 8.8)
- [CVE-2019-12569](https://insights.sbomify.com/CVE-2019-12569/): Path traversal in n/a (high 7.8)
- [CVE-2020-14049](https://insights.sbomify.com/CVE-2020-14049/): Other in n/a (high 7.5)
- [CVE-2025-55996](https://insights.sbomify.com/CVE-2025-55996/): Cross-site scripting in n/a (medium 6.3)
- [CVE-2018-3987](https://insights.sbomify.com/CVE-2018-3987/): Information disclosure in Rakuten Viber (medium 4.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-13476 and fix it if it is affected.

What it is: CVE-2025-13476 is a critical vulnerability in Rakuten Viber Cloak - Android, published on 5 Mar 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-2025-13476 in the wild and no public exploit code.

Affected product: Rakuten Viber Cloak - Android. 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-2025-13476/ (Markdown: https://insights.sbomify.com/CVE-2025-13476/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-13476
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-13476
- OSV: https://osv.dev/vulnerability/CVE-2025-13476

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-13476/
Summaries are generated and may contain mistakes; the official description above is the record.