Critical ZIP File Vulnerabilities: Why You Must Upgrade 7-Zip Now

ZIP files are one of the oldest and most common ways to share documents, photos, installers, and backups. Because ZIP is everywhere, from email attachments to cloud storage, attackers love to target it. Recent discoveries have exposed dangerous security flaws in unpatched compression tools — especially older versions of 7-Zip, WinRAR, and built-in Windows ZIP extractors.

If you haven’t updated 7-Zip recently (or if you’re still running versions older than 22.x), your system may be vulnerable to:

Remote code execution (RCE)
Privilege escalation
Path traversal attacks
Hidden malware inside archives
Supply-chain exploits that run during extraction

This article explains the risks, how attackers use ZIP weaknesses, and why upgrading 7-Zip is no longer optional — it’s essential.

1. ZIP Files Are a Perfect Target for Hackers

ZIP is so old and universal that most people open ZIP files without thinking.

Valid Image — ZIP Icon (Public Domain)

Attackers take advantage of this trust.

Unlike executable files, ZIPs rarely trigger suspicion. People open them quickly because they:

Expect them from coworkers
Download them from websites
Receive them inside email attachments
Use them to share photos or documents

But inside a ZIP, malicious files can hide in plain sight.

2. The “ZIP Path Traversal” Exploit — A Serious Threat

One of the oldest and most dangerous ZIP-related vulnerabilities is path traversal.

This happens when attackers craft a ZIP that contains paths like:

../../../../Windows/System32/hack.exe

If your archive tool doesn’t sanitize paths, the extraction process may write files:

Outside the destination folder
Into system directories
Overwriting critical files

Older versions of 7-Zip did not properly validate these paths in several edge cases.

Meaning:

A single extraction click could overwrite system files or install malware silently.

3. The DLL Hijacking Vulnerability in 7-Zip

In early vulnerability reports, security researchers found that 7-Zip’s help file system was loading DLLs incorrectly. This allowed attackers to:

Place malicious DLLs next to 7zFM.exe
Trigger code execution when the user opened the help menu

Valid Image — DLL File Example (Public Domain)

While the bug looks harmless, attackers weaponized it in phishing campaigns.

With a normal-looking ZIP attached to an email:

User extracts
Malicious DLL drops next to 7-Zip
Opening 7-Zip triggers the malware

This exploit has been patched — but only if you’ve updated.

4. Exploits Using “ZIP Bombs” and Resource Attacks

A ZIP bomb is a tiny archive that expands into massive data during extraction.

Example:

42 KB ZIP → expands to 4.5 petabytes

These aren’t “accidents.” Hackers use ZIP bombs to:

Crash antivirus programs
Freeze computers
Exhaust server memory
Sneak malware while systems are overloaded

Valid Image — CPU and Memory Load (Public Domain)

Older tools like outdated versions of 7-Zip and WinRAR are more vulnerable to these attacks because they:

Didn’t cap recursion depth
Didn’t validate compression ratios
Didn’t detect malicious nested archives

Modern 7-Zip versions add protections — but only if you update.

5. Malicious Scripts Hidden Inside ZIP Files

Attackers often hide:

JavaScript (.js)
Batch files (.bat)
PowerShell (.ps1)
Macros (.docm)
Fake PDF files

inside ZIP archives.

Valid Image — File Types That Can Hide Malware (Public Domain)

Unpatched 7-Zip versions sometimes:

Failed to warn users - Displayed misleading file preview info - Allowed double extensions to hide file types (e.g., invoice.pdf.exe)

Modern versions significantly improve protections.

6. How Attackers Use ZIP Phishing Kits

Modern phishing attacks often use ZIP files because:

They bypass email filters more easily
They compress malware to avoid detection
They bundle multiple payloads
Victims trust them

A typical attack flow:

You receive a “FedEx Notice” or “Invoice Due” email.
A ZIP attachment is included.
Inside is a malicious JavaScript or EXE file.
Older 7-Zip versions display no warning.
You double-click and your device becomes compromised.

More than 65% of email malware today arrives in compressed archives.

7. Why Upgrading 7-Zip Is Urgent

7-Zip is a great open-source tool — but like all software, it needs updates.

Security patches over the last few years fixed:

DLL hijacking flaws
Path traversal bugs
Incorrect privilege handling
Archive parsing issues
Crashes due to malformed archives

If you're running anything before 22.x, you may be missing critical patches.

Valid Image — 7-Zip Logo (Fair Use Placeholder)

(Wikimedia does not host the official 7-Zip logo, so no image included here to avoid invalid links.)

8. How to Check Your Current 7-Zip Version

Open 7-Zip File Manager 2. Click Help → About 3. Look at the version number

If it is older than:

22.x for Windows - 22.x for Linux/macOS ports

…you need to upgrade immediately.

9. How to Upgrade 7-Zip Safely

Only download from the official website: https://www.7-zip.org/

NEVER download from:

“Free download” sites - Third-party mirrors - Software bundle websites - Pop-ups claiming “Your ZIP extractor is outdated”

Those sites often include:

Malware - Adware - Spyware - Injected installers

10. What About WinRAR and Windows Explorer?

WinRAR WinRAR has had multiple serious RCE vulnerabilities over the years. Always update to the latest version.

Windows built-in ZIP extractor

Safer than it used to be, but still more limited than 7-Zip. It does not protect against all advanced attacks.

11. Tips to Stay Safe When Opening ZIP Files

Update 7-Zip or WinRAR immediately - Never open ZIP files from unknown senders - Check the actual file extension (beware .pdf.exe)
Scan ZIPs with antivirus before extraction - Don’t extract directly to system folders - Be cautious of ZIPs with only a single file inside
Avoid ZIPs that contain scripts or EXE files

Valid Image — Warning Sign (Public Domain)

Final Thoughts: ZIP Safety Starts With One Click — Update Now

ZIP files are not dangerous on their own. The danger comes from outdated software that handles them incorrectly.

7-Zip is widely trusted, but trust does not replace updates. Attackers prey on people who delay upgrades because older versions still work “well enough.”

The truth is simple:

If your ZIP extractor is out of date, your whole system is at risk.

A fast upgrade keeps you protected from:

ZIP bombs - RCE exploits - Path traversal attacks - DLL hijacking - Malware hidden in archives

Update 7-Zip today — and stay one step ahead of attackers.