# CVE-2020-8617: A logic error in code which checks TSIG validity can be used to trigger an assertion failure in tsig.c

> An attacker can cause a BIND DNS server to crash by sending a specially crafted message that triggers an assertion failure in TSIG validation.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 May 2020
- **Updated:** 16 Sep 2024
- **Also known as:** ALPINE-CVE-2020-8617, DEBIAN-CVE-2020-8617, GHSA-q6g5-8p95-hqh7, RHSA-2020:2893, UBUNTU-CVE-2020-8617

## What is CVE-2020-8617?

CVE-2020-8617 is a high-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 19 May 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Using a specially-crafted message, an attacker may potentially cause a BIND server to reach an inconsistent state if the attacker knows (or successfully guesses) the name of a TSIG key used by the server. Since BIND, by default, configures a local session key even on servers whose configuration does not otherwise make use of it, almost all current BIND servers are vulnerable. In releases of BIND dating from March 2018 and after, an assertion check in tsig.c detects this inconsistent state and deliberately exits. Prior to the introduction of the check the server would continue operating in an inconsistent state, with potentially harmful results.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2020-8617?

It affects 5 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bind` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-chroot` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-debuginfo` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-devel` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-export-devel` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-export-libs` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-libs` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-libs-lite` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-license` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-lite-devel` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11-devel` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11-libs` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11-utils` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-sdb` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-sdb-chroot` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-utils` | Red Hat:rhel_eus:7.7::computenode | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-chroot` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-debuginfo` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-devel` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-export-devel` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-export-libs` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-libs` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-libs-lite` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-license` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-lite-devel` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11-devel` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11-libs` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-pkcs11-utils` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-sdb` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-sdb-chroot` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |
| `bind-utils` | Red Hat:rhel_eus:7.7::server | All versions | 32:9.11.4-9.P2.el7_7.1 |

Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Isc Bind, Opensuse Leap.

## How do I fix CVE-2020-8617?

Apply the vendor's patch.

## Is CVE-2020-8617 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-8617 exists.

Public exploit code:

- PoC for CVE-2020-8617 (BIND) (github_poc): https://github.com/knqyf263/CVE-2020-8617
- BIND TSIG Badtime Query Denial of Service (metasploit)
- BIND - 'TSIG' Denial of Service (exploitdb)
- https://github.com/gothburz/cve-2020-8617 (github_poc): https://github.com/gothburz/cve-2020-8617

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-8617 and fix it if it is affected.

What it is: CVE-2020-8617 is a high-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 19 May 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-8617 exists.

Affected product: Canonical Ubuntu Linux. 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-2020-8617/ (Markdown: https://insights.sbomify.com/CVE-2020-8617/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-8617
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-8617
- OSV: https://osv.dev/vulnerability/CVE-2020-8617

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-8617/
Summaries are generated and may contain mistakes; the official description above is the record.