CVE-2021-23856CWE-79

Reflected Cross-Site-Scripting

Critical · published October 4, 2021

CVSS v3.1
10.0
EPSS
1%
Percentile
49.5
In the wild
Unconfirmed
What it is

🚨 A crafty URL is all an attacker needs to execute scripts on unsuspecting clients! This reflected XSS vulnerability could make your users' devices act like puppets. 🔥 Imagine a restaurant where the waitress takes a suspicious order from a customer and serves it to the diners. That’s what happens here — the web server blindly serves a URL without checking if it’s safe, allowing harmful scripts to slip right in! If an attacker gets their hands on a manipulated URL, they could unleash scripts on your clients' devices, potentially stealing sensitive data, hijacking sessions, or even spreading malware. This is not just a minor inconvenience; it could lead to a complete compromise of users' systems, making it absolutely devastating!

Put simply

Imagine a restaurant where the waitress takes a suspicious order from a customer and serves it to the diners. That’s what happens here — the web server blindly serves a URL without checking if it’s safe, allowing harmful scripts to slip right in! This reflected XSS vulnerability occurs when the web server does not properly sanitize user input in URLs. As a result, malicious scripts can execute in the browsers of clients who click on the affected URL, leading to serious security risks.

What to do

If an attacker gets their hands on a manipulated URL, they could unleash scripts on your clients' devices, potentially stealing sensitive data, hijacking sessions, or even spreading malware. This is not just a minor inconvenience; it could lead to a complete compromise of users' systems, making it absolutely devastating! Immediately update the web server to the latest version to patch this vulnerability. Implement proper input validation and output encoding on all user-generated content to prevent similar issues. Regularly review and test for XSS vulnerabilities as part of your security practice. You've got this! By addressing this vulnerability, you're stepping up as a security hero and protecting your users! 🦸‍♂️

The record
Technical detail
CVSS v3.1
10.0 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00629 · 49.5th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2021-10-04T17:32Z
EPSS history
Timeline
  • 04 OCT 17:32Z
    Reflected Cross-Site-Scripting
    cvelistv5