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MEDIUM severity

GHSA-2v5f-23xc-v9qr

MEDIUMFix: drudru/ansi_up@c8c726e

GHSA-2v5f-23xc-v9qr is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in ansi_up. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether GHSA-2v5f-23xc-v9qr is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

ansi_up cross-site scripting vulnerability

Also known asCVE-2021-3377
Published
Mar 11, 2021
Updated
Nov 4, 2025
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 4, 2025 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

153other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
ansi_upnpm
160Kdownloads / week

Description

The npm package ansi_up converts ANSI escape codes into HTML. In ansi_up v4, ANSI escape codes can be used to create HTML hyperlinks. Due to insufficient URL sanitization, this feature is affected by a cross-site scripting (XSS) vulnerability. This issue is fixed in v5.0.0.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmansi_upall versions5.0.0
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ansi_up. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update ansi_up to 5.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-2v5f-23xc-v9qr is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-2v5f-23xc-v9qr is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-2v5f-23xc-v9qr. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

The npm package ansi_up converts ANSI escape codes into HTML. In ansi_up v4, ANSI escape codes can be used to create HTML hyperlinks. Due to insufficient URL sanitization, this feature is affected by a cross-site scripting (XSS) vulnerability. This issue is fixed in v5.0.0.
O3 Security · Impact-Aware SCA

Is GHSA-2v5f-23xc-v9qr in your dependencies?

O3 detects GHSA-2v5f-23xc-v9qr across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

GHSA-2v5f-23xc-v9qr: ansi_up cross-site… | O3 Security