CVE-2021-43523

What it is

In uClibc and uClibc-ng before 1.0.39, incorrect handling of special characters in domain names returned by DNS servers via gethostbyname, getaddrinfo, gethostbyaddr, and getnameinfo can lead to output of wrong hostnames (leading to domain hijacking) or injection into applications (leading to remote code execution, XSS, applications crashes, etc.). In other words, a validation step, which is expected in any stub resolver, does not occur.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure, data tampering, service disruption.

Exploit odds

3.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-11-10 15:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:11 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.1% in the next 30 days (EPSS).
• Severity: 9.6 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-11-10 15:15 UTC

Last modified

2026-06-17 04:11 UTC

Exploit probability

3.1% · EPSS, next 30 days

Weakness

CWE-79 · Cross-site scripting

Record status

Modified

Affected

• Uclibc ≤ 0.9.33.2
• uclibc-ng Project uclibc-ng < 1.0.39

Attack profile CVSS 3.1 · 9.6

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-43523.md and follow it. Check whether this project is affected by CVE-2021-43523. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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