# CVE-2020-15093: Improper verification of signature threshold in tough

> An attacker can bypass TUF signature threshold verification by duplicating valid signatures, allowing unauthorized metadata acceptance in the tough library.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Jul 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-5q2r-92f9-4m49, RUSTSEC-2020-0024

## What is CVE-2020-15093?

CVE-2020-15093 is a high-severity vulnerability in awslabs tough, published on 9 Jul 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The tough library (Rust/crates.io) prior to version 0.7.1 does not properly verify the threshold of cryptographic signatures. It allows an attacker to duplicate a valid signature in order to circumvent TUF requiring a minimum threshold of unique signatures before the metadata is considered valid. A fix is available in version 0.7.1. CVE-2020-6174 is assigned to the same vulnerability in the TUF reference implementation.

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

## Which versions are affected by CVE-2020-15093?

3 open source packages ship an affected version, including tough. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `tough` | crates.io | All versions | 0.7.1 |
| `tough` | crates.io | All versions | 0.7.1 |
| `tough` | crates.io | From 0.0.0-0 | 0.7.1 |

Products: Amazon Tough.

## How do I fix CVE-2020-15093?

Upgrade tough to 0.7.1 or later.

## Is CVE-2020-15093 being exploited?

There is no known exploitation of CVE-2020-15093 in the wild and no public exploit code.

## Other vulnerabilities in awslabs tough

- [CVE-2021-41149](https://insights.sbomify.com/CVE-2021-41149/): Improper sanitization of target names in tough (high 8.2)
- [CVE-2021-41150](https://insights.sbomify.com/CVE-2021-41150/): Improper sanitization of delegated role names in tough (high 8.2)
- [CVE-2026-6967](https://insights.sbomify.com/CVE-2026-6967/): Missing Delegated Metadata Validation in awslabs/tough (high 7.1)
- [CVE-2026-6968](https://insights.sbomify.com/CVE-2026-6968/): Multiple Path Traversal Variants in awslabs/tough (high 7.1)
- [CVE-2026-6966](https://insights.sbomify.com/CVE-2026-6966/): Signature Threshold Bypass in awslabs/tough Delegated Roles (high 7.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-15093 and fix it if it is affected.

What it is: CVE-2020-15093 is a high-severity vulnerability in awslabs tough, published on 9 Jul 2020. 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-2020-15093 in the wild and no public exploit code.

Affected packages and fixed versions:
- tough (crates.io): affected all versions; fixed in 0.7.1
- tough (crates.io): affected all versions; fixed in 0.7.1
- tough (crates.io): affected from 0.0.0-0; fixed in 0.7.1

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-2020-15093/ (Markdown: https://insights.sbomify.com/CVE-2020-15093/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15093
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15093
- OSV: https://osv.dev/vulnerability/CVE-2020-15093

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15093/
Summaries are generated and may contain mistakes; the official description above is the record.