CVE-2021-3377

Exp

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.

Published: 2021-03-05 Last update: 2025-11-03 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3377 is rated High Exploit Risk (78.8/100): CVSS Medium severity, with high exploitation likelihood (EPSS 59.25%, 98th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +22.39% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-3377

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-3377

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-16 36.86% 59.25% +22.39%
2 2026-03-03 46.14% 36.86% -9.28%
3 2025-12-17 — 46.14% —

Full EPSS history (21 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3377

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-3377

GitHub Security Advisory for CVE-2021-3377

GHSA-2v5f-23xc-v9qr · Severity: medium · Ecosystem: npm — ansi_up cross-site scripting vulnerability

OS Trackers for CVE-2021-3377

vendor priority summary link
debian not yet assigned CVE-2021-3377 not yet assigned priority: Debian including 1 source packages (node-ansi-up), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-3377
redhat medium — https://access.redhat.com/security/cve/CVE-2021-3377
ubuntu medium CVE-2021-3377 medium priority: Ubuntu including 1 source packages (node-ansi-up), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 6, ignored 4, DNE 3, needs-triage 2, released 1. https://ubuntu.com/security/CVE-2021-3377

Affected software / configurations for CVE-2021-3377

Vendor Product Version Raw CPE
ansi_up_project ansi_up < 5.0.0 cpe:2.3:a:ansi_up_project:ansi_up:*:*:*:*:*:node.js:*:*

References for CVE-2021-3377

cvelogic Threat Intelligence