CVE-2025-59364VulnerabilityPublished 14 Sep 2025Updated 15 Sep 2025

CVE-2025-59364: Express XSS Sanitizer · Uncontrolled Recursion

Affects Express XSS SanitizerSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Express XSS Sanitizer project Express XSS Sanitizer	Affected =2.0.0	Fixed in–

AI-suggested

To mitigate this vulnerability, European organizations should first identify any usage of the Express XSS Sanitizer package version 2.0.0 within their Node.js applications. 2) Implement input validation and size limits on JSON request bodies at the application or API gateway level to prevent excessively nested or large payloads that could trigger recursion. 3) Employ runtime protections such as limiting the maximum call stack size or using Node.js process monitoring to detect and mitigate abnormal resource consumption. 4) Monitor application logs and network traffic for unusual patterns indicative of recursive payload attempts. 5) Engage with the Express XSS Sanitizer maintainers or community to track patch releases and apply updates promptly once available. 6) Conduct security testing, including fuzzing and recursive input testing, to identify similar recursion vulnerabilities in custom sanitization code. These targeted measures go beyond generic advice by focusing on controlling recursion depth, input size, and alternative sanitization strategies.

Description

The express-xss-sanitizer (aka Express XSS Sanitizer) package through 2.0.0 for Node.js has an unbounded recursion depth in sanitize in lib/sanitize.js for a JSON request body.

Impact

For European organizations, the primary impact of this vulnerability is the potential for denial-of-service attacks against web applications that utilize the Express XSS Sanitizer package version 2.0.0. Such DoS attacks can disrupt business operations, degrade service availability, and damage reputation, especially for organizations relying on Node.js-based web services for customer-facing portals, APIs, or internal tools. While the vulnerability does not lead to data breaches or unauthorized data modification, service outages can result in financial losses and compliance issues under regulations like GDPR if service interruptions affect data processing or availability commitments. Organizations in sectors with high availability requirements, such as finance, healthcare, and e-commerce, are particularly vulnerable. Additionally, the ease of exploitation without authentication or user interaction increases the attack surface, making automated scanning and exploitation feasible by threat actors. The lack of known exploits currently provides a window for proactive mitigation before widespread attacks occur.

CWE-674Uncontrolled Recursion (opens in a new tab)
Class weakness
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
Implementation
Ensure that an end condition will be reached under all logic conditions. The end condition may include checking against the depth of recursion and exiting with an error if the recursion goes too deep. The complexity of the end condition contributes to the effectiveness of this action.
Implementation
Increase the stack size.
Attack patterns
Serialized Data with Nested Payloads (opens in a new tab)
Oversized Serialized Data Payloads (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 22 Sep 2025, 00:37 UTC

WeaknessesCWE-674

Technical details

References

Community reviews

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