CVE-2009-4142

What it is

The htmlspecialchars function in PHP before 5.2.12 does not properly handle (1) overlong UTF-8 sequences, (2) invalid Shift_JIS sequences, and (3) invalid EUC-JP sequences, which allows remote attackers to conduct cross-site scripting (XSS) attacks by placing a crafted byte sequence before a special character.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

6.5% chance of exploitation in the next 30 days (EPSS).

Fix

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

Timeline

1. 2009-12-21 16:30 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-16 23:13 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 6.5% in the next 30 days (EPSS).
• Severity: 4.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2009-12-21 16:30 UTC

Last modified

2026-06-16 23:13 UTC

Exploit probability

6.5% · EPSS, next 30 days

Weakness

CWE-79 · Cross-site scripting

Record status

Modified

Affected

• PHP ≤ 5.2.11
• PHP 1.0
• PHP 2.0
• PHP 2.0b10
• PHP 3.0
• PHP 3.0.1
• PHP 3.0.2
• PHP 3.0.3

Attack profile CVSS 2.0 · 4.3

Attack vector

Network

Complexity

Medium

Authentication

None

Confidentiality

None

Integrity

Partial

Availability

None

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-2009-4142.md and follow it. Check whether this project is affected by CVE-2009-4142. 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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