CVE-2021-26505

Prototype pollution vulnerability in MrSwitch hello.js version 1.18.6, allows remote attackers to execute arbitrary code via hello.utils.extend function.

Published: 2023-08-11 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-26505 is rated Moderate Risk (58.3/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 0.95%). Review affected assets and schedule remediation.

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

Exploit prediction scoring system (EPSS) score for CVE-2021-26505

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 2026-06-15 1.67% 0.95% -0.72%
2 2026-05-06 1.26% 1.67% +0.41%
3 2025-11-21 — 1.26% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-26505

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H 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:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]

Weakness enumeration for CVE-2021-26505

GitHub Security Advisory for CVE-2021-26505

GHSA-g3vf-47fv-8f3c · Severity: critical · Ecosystem: npm — MrSwitch hello.js vulnerable to prototype pollution

Affected software / configurations for CVE-2021-26505

Vendor Product Version Raw CPE
hello.js_project hello.js 1.18.6 cpe:2.3:a:hello.js_project:hello.js:1.18.6:*:*:*:*:node.js:*:*

References for CVE-2021-26505

cvelogic Threat Intelligence