# CVE-2026-105221: Gist RubyGem before 6.1.0 Disabled TLS Certificate Verification

> An on-path attacker can intercept HTTPS traffic to steal OAuth tokens and credentials by exploiting disabled TLS certificate verification in the Gist RubyGem.

- **Severity:** Critical 9.1 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Oct 2026
- **Updated:** 5 Oct 2026
- **Also known as:** GHSA-phqh-xp3p-h6mr, UBUNTU-CVE-2026-105221

## What is CVE-2026-105221?

CVE-2026-105221 is a critical vulnerability in defunkt gist, published on 4 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The gist RubyGem before 6.1.0 contains an improper certificate validation vulnerability that allows on-path attackers to intercept HTTPS traffic because http_connection in lib/gist.rb sets VERIFY_NONE. Attackers can present any certificate to read or modify GitHub API traffic, stealing OAuth tokens and login credentials to read and modify the victim's gists.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-105221?


## How do I fix CVE-2026-105221?

No fix has been published for CVE-2026-105221 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-105221 being exploited?

There is no known exploitation of CVE-2026-105221 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-105221 - gist RubyGem - High - MITM - GitHub OAuth token theft (github_poc): https://github.com/abraxas/cve-2026-105221-gist-tls

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-105221 and fix it if it is affected.

What it is: CVE-2026-105221 is a critical vulnerability in defunkt gist, published on 4 Oct 2026. 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-2026-105221 in the wild and no public exploit code.

Affected product: defunkt gist. 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-2026-105221/ (Markdown: https://insights.sbomify.com/CVE-2026-105221/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-105221
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-105221
- OSV: https://osv.dev/vulnerability/CVE-2026-105221

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-105221/
Summaries are generated and may contain mistakes; the official description above is the record.