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CVE-2021-26505

CVE-2021-26505: MrSwitch hello.js vulnerable to prototype pollution

9.8

CVSS Score
3.1

Basic Information

CVE ID
CVE-2021-26505
GHSA ID
GHSA-g3vf-47fv-8f3c
EPSS Score
0.78559%
CWE
CWE-1321
Published
8/11/2023
Updated
11/9/2023
KEV Status
No
Technology
TechnologyJavaScript

Technical Details

CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Package NameEcosystemVulnerable VersionsFirst Patched Version
hellojsnpm< 1.18.81.18.8

Vulnerability Intelligence
Miggo AIMiggo AI

Miggo AIRoot Cause Analysis

  1. The vulnerability documentation explicitly names hello.utils.extend as the entry point
  2. The GitHub issue #634 shows vulnerable code patterns in this function's recursive merge logic
  3. The commit fix adds prototype pollution guards (proto/constructor checks) directly in this function
  4. The CVE description confirms exploitation occurs via this utility function
  5. The function's purpose (deep object merging) matches classic prototype pollution patterns when unsafe recursion is used

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

WAF Protection Rules

WAF Rule

* prototyp* pollution vuln*r**ility in MrSwit** **llo.js prior to v*rsion *.**.* *llows r*mot* *tt**k*rs to *x**ut* *r*itr*ry *o** vi* `**llo.utils.*xt*n*` *un*tion.

Reasoning

*. T** vuln*r**ility *o*um*nt*tion *xpli*itly n*m*s **llo.utils.*xt*n* *s t** *ntry point *. T** *it*u* issu* #*** s*ows vuln*r**l* *o** p*tt*rns in t*is *un*tion's r**ursiv* m*r** lo*i* *. T** *ommit *ix ***s prototyp* pollution *u*r*s (__proto__/*o