# CVE-2020-27347: tmux stack buffer overflow in function input_csi_dispatch_sgr_colon

> A stack-based buffer overflow in tmux allows attackers to execute arbitrary code via malicious terminal output.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Nov 2020
- **Updated:** 17 Sep 2024
- **Also known as:** ALPINE-CVE-2020-27347, DEBIAN-CVE-2020-27347, GHSA-xp5q-c655-9565, JLSEC-2026-528, UBUNTU-CVE-2020-27347, USN-4618-1

## What is CVE-2020-27347?

CVE-2020-27347 is a high-severity memory corruption vulnerability in Ubuntu tmux, published on 6 Nov 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In tmux before version 3.1c the function input_csi_dispatch_sgr_colon() in file input.c contained a stack-based buffer-overflow that can be exploited by terminal output.

Weakness: CWE-787 (Out-of-bounds Write), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2020-27347?

It affects 1 product.


Products: Tmux Project Tmux.

## How do I fix CVE-2020-27347?

Upgrade to a fixed version.

## Is CVE-2020-27347 being exploited?

There is no known exploitation of CVE-2020-27347 in the wild and no public exploit code.

Public exploit code:

- Enhanced fuzzing for tmux using OSS-Fuzz. Includes custom `cmd-fuzzer` and `argument-fuzzer` harnesses for improved code coverage and a PoC for `CVE-2020-27347` (github_poc): https://github.com/lucadibello/tmux-fuzzing

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27347 and fix it if it is affected.

What it is: CVE-2020-27347 is a high-severity memory corruption vulnerability in Ubuntu tmux, published on 6 Nov 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-27347 in the wild and no public exploit code.

Affected product: Ubuntu tmux. 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-2020-27347/ (Markdown: https://insights.sbomify.com/CVE-2020-27347/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27347
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27347
- OSV: https://osv.dev/vulnerability/CVE-2020-27347

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-27347/
Summaries are generated and may contain mistakes; the official description above is the record.