# CVE-2020-5300: Disallow replay of `private_key_jwt` by blacklisting JTIs in Hydra

> Hydra fails to enforce unique JTI values in private_key_jwt authentication, allowing potential token replay attacks if intercepted.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 Apr 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-3p3g-vpw6-4w66, GO-2022-0786

## What is CVE-2020-5300?

CVE-2020-5300 is a medium-severity vulnerability in ory hydra, published on 6 Apr 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

In Hydra (an OAuth2 Server and OpenID Certified™ OpenID Connect Provider written in Go), before version 1.4.0+oryOS.17, when using client authentication method 'private_key_jwt' [1], OpenId specification says the following about assertion `jti`: "A unique identifier for the token, which can be used to prevent reuse of the token. These tokens MUST only be used once, unless conditions for reuse were negotiated between the parties". Hydra does not check the uniqueness of this `jti` value. Exploiting this vulnerability is somewhat difficult because: - TLS protects against MITM which makes it difficult to intercept valid tokens for replay attacks - The expiry time of the JWT gives only a short window of opportunity where it could be replayed This has been patched in version v1.4.0+oryOS.17

Weakness: CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2020-5300?

3 open source packages ship an affected version, including github.com/ory/hydra. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/ory/hydra` | Go | All versions | 1.4.0 |
| `github.com/ory/hydra` | Go | All versions | 1.4.0 |
| `github.com/ory/hydra` | Go | All versions | 1.4.0 |

Products: Ory Hydra.

## How do I fix CVE-2020-5300?

Upgrade github.com/ory/hydra to 1.4.0 or later.

## Is CVE-2020-5300 being exploited?

There is no known exploitation of CVE-2020-5300 in the wild and no public exploit code.

## Other vulnerabilities in ory hydra

- [CVE-2026-33504](https://insights.sbomify.com/CVE-2026-33504/): Ory Hydra has a SQL injection via forged pagination tokens (high 7.2)
- [CVE-2019-8400](https://insights.sbomify.com/CVE-2019-8400/): Hydra has Reflected XSS via error_hint parameter (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-5300 and fix it if it is affected.

What it is: CVE-2020-5300 is a medium-severity vulnerability in ory hydra, published on 6 Apr 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-5300 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/ory/hydra (Go): affected all versions; fixed in 1.4.0
- github.com/ory/hydra (Go): affected all versions; fixed in 1.4.0
- github.com/ory/hydra (Go): affected all versions; fixed in 1.4.0

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-2020-5300/ (Markdown: https://insights.sbomify.com/CVE-2020-5300/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-5300
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-5300
- OSV: https://osv.dev/vulnerability/CVE-2020-5300

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-5300/
Summaries are generated and may contain mistakes; the official description above is the record.