# CVE-2019-20786: Improper Authenication in Pion DTLS

> Attackers can inject unencrypted data after handshake completion in Pion DTLS due to missing epoch checks, bypassing encryption guarantees.

- **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:** Yes
- **Published:** 19 Apr 2020
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-7gfg-6934-mqq2, GO-2020-0038

## What is CVE-2019-20786?

CVE-2019-20786 is a critical vulnerability in n/a, published on 19 Apr 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

handleIncomingPacket in conn.go in Pion DTLS before 1.5.2 lacks a check for application data with epoch 0, which allows remote attackers to inject arbitrary unencrypted data after handshake completion.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2019-20786?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/pion/dtls` | Go | All versions | 1.5.2 |
| `github.com/pion/dtls` | Go | All versions | 1.5.2 |
| `github.com/pion/dtls` | Go | All versions | 1.5.2 |

Products: Pion Dtls.

## How do I fix CVE-2019-20786?

Upgrade github.com/pion/dtls to 1.5.2 or later.

## Is CVE-2019-20786 being exploited?

There is no known exploitation of CVE-2019-20786 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2022-29190](https://insights.sbomify.com/CVE-2022-29190/): Header reconstruction method can be thrown into an infinite loop in Pion DTLS (high 7.5)
- [CVE-2026-26014](https://insights.sbomify.com/CVE-2026-26014/): Pion DTLS uses random nonce generation with AES GCM ciphers risks leaking the authentication key (medium 5.9)
- [CVE-2022-29222](https://insights.sbomify.com/CVE-2022-29222/): Improper Certificate Validation in Pion DTLS (medium 5.9)
- [CVE-2022-29189](https://insights.sbomify.com/CVE-2022-29189/): Buffer for inbound DTLS fragments has no limit (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-20786 and fix it if it is affected.

What it is: CVE-2019-20786 is a critical vulnerability in n/a, published on 19 Apr 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-2019-20786 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/pion/dtls (Go): affected all versions; fixed in 1.5.2
- github.com/pion/dtls (Go): affected all versions; fixed in 1.5.2
- github.com/pion/dtls (Go): affected all versions; fixed in 1.5.2

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-2019-20786/ (Markdown: https://insights.sbomify.com/CVE-2019-20786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-20786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-20786
- OSV: https://osv.dev/vulnerability/CVE-2019-20786

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-20786/
Summaries are generated and may contain mistakes; the official description above is the record.