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PhpSpreadsheet has an Unauthenticated Cross-Site-Scripting (XSS) in sample file

Moderate severity GitHub Reviewed Published Oct 6, 2024 in PHPOffice/PhpSpreadsheet • Updated Oct 7, 2024

Package

composer phpoffice/phpspreadsheet (Composer)

Affected versions

>= 2.2.0, < 2.3.0
< 1.29.2
>= 2.0.0, < 2.1.1

Patched versions

2.3.0
1.29.2
2.1.1

Description

Summary

One of the sample scripts in PhpSpreadsheet is susceptible to a cross-site scripting (XSS) vulnerability due to improper handling of input where a number is expected leading to formula injection.

Details

The following code in 45_Quadratic_equation_solver.php concatenates the user supplied parameters directly into spreadsheet formulas. This allows an attacker to take control over the formula and output unsanitized data into the page, resulting in JavaScript execution.

$discriminantFormula = '=POWER(' . $_POST['B'] . ',2) - (4 * ' . $_POST['A'] . ' * ' . $_POST['C'] . ')';
$discriminant = Calculation::getInstance()->calculateFormula($discriminantFormula);

$r1Formula = '=IMDIV(IMSUM(-' . $_POST['B'] . ',IMSQRT(' . $discriminant . ')),2 * ' . $_POST['A'] . ')';
$r2Formula = '=IF(' . $discriminant . '=0,"Only one root",IMDIV(IMSUB(-' . $_POST['B'] . ',IMSQRT(' . $discriminant . ')),2 * ' . $_POST['A'] . '))';

PoC

  1. Access 45_Quadratic_equation_solver.php in a browser
  2. Enter any valid values for for b and c, and enter the following for a
1) & ("1)),1)&char(60)&char(105)&char(109)&char(103)&char(32)&char(115)&char(114)&char(99)&char(61)&char(120)&char(32)&char(111)&char(110)&char(101)&char(114)&char(114)&char(111)&char(114)&char(61)&char(97)&char(108)&char(101)&char(114)&char(116)&char(40)&char(41)&char(62)&POWER(((1") &n("1")&(1
  1. Press submit and observe that JavaScript is executed.

exploit-phpspreadsheet

Impact

The impact of this vulnerability on the project is expected to be relatively low since these are sample files that should not be included when the library is used properly (e.g., through composer). However, at least two instances of popular WordPress plugins have unintentionally exposed this file by including the entire git repository. Since these files also serve as reference points for developers using the library, addressing this issue can enhance security for users.

A solution to fix the vulnerability is proposed below, and a request for a CVE assignment has been made to facilitate responsible disclosure of the security issue to the affected WordPress plugins.

Remediation

A quick and easy solution to prevent this attack is to force the parameters to be numerical values:

if (isset($_POST['submit'])) {
    $_POST['A'] = floatval($_POST['A']);
    $_POST['B'] = floatval($_POST['B']);
    $_POST['C'] = floatval($_POST['C']);
    if ($_POST['A'] == 0) {

Thank you for your time!

References

@oleibman oleibman published to PHPOffice/PhpSpreadsheet Oct 6, 2024
Published to the GitHub Advisory Database Oct 7, 2024
Reviewed Oct 7, 2024
Published by the National Vulnerability Database Oct 7, 2024
Last updated Oct 7, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction Passive
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality Low
Integrity Low
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

EPSS score

0.046%
(18th percentile)

Weaknesses

CVE ID

CVE-2024-45060

GHSA ID

GHSA-v66g-p9x6-v98p

Source code

Credits

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