VulnerabilityPublished 15 Mar 2026Updated 16 Mar 2026

CVE-2026-4171: CodeGenieApp serverless-express · Authorization Bypass

Affects CodeGenieApp serverless-expressSource CVE Database V5

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Public exploit available · CVSS 5.3 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

5.3Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system 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 Vulnerable System 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 Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
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), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity 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
CodeGenieAppserverless-express	Affected =4.17.0 =4.17.1	Fixed in–
npmserverless-express`pkg:npm/serverless-express`Other threats	Affected =4.17.0 =4.17.1	Fixed in–

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AI-suggested

To mitigate this vulnerability, organizations should immediately audit and review all API endpoints that accept userId or similar parameters to ensure strict validation and authorization checks are enforced server-side. Implement robust access control mechanisms that verify the identity and permissions of the requester against the requested userId before processing any actions. Employ input validation and sanitization to prevent parameter tampering. If feasible, upgrade to a non-vulnerable version of serverless-express once a patch is released or consider applying custom patches to fix the authorization logic in the TodoList.ts file. Additionally, monitor logs for unusual access patterns or unauthorized attempts to manipulate userId parameters. Employ runtime application self-protection (RASP) or web application firewalls (WAF) with rules targeting suspicious parameter manipulation as an interim defense. Finally, maintain close communication with the vendor or community for updates and patches.

Description

CVE-2026-4171 is an authorization bypass vulnerability in CodeGenieApp's serverless-express versions up to 4.17.1. The flaw exists in the API Endpoint component, specifically in the handling of the userId argument within the TodoList.ts file. This vulnerability allows remote attackers to manipulate userId values to bypass authorization controls without authentication or user interaction. Although the vendor has not responded to the disclosure, no known exploits are currently observed in the wild. The CVSS 4.0 score rates this as a medium severity issue due to its remote exploitability and partial impact on confidentiality, integrity, and availability. Organizations using affected versions should prioritize code review and implement strict validation of userId parameters to mitigate risk.

Impact

This vulnerability poses a significant risk to organizations using the affected versions of CodeGenieApp serverless-express, especially those relying on the vulnerable API endpoints for managing user data or tasks. Unauthorized access through userId manipulation can lead to data leakage, unauthorized data modification, or disruption of service availability. In multi-tenant or cloud environments, this could allow attackers to escalate privileges or access other users' data, undermining trust and compliance with data protection regulations. The lack of vendor response and patch availability increases the window of exposure, potentially inviting attackers to develop exploits. Organizations with sensitive or critical workloads running on serverless architectures using this framework are particularly at risk, as the vulnerability can be exploited remotely without user interaction or complex attack vectors.

Summary

CVE-2026-4171 identifies an authorization bypass vulnerability in the CodeGenieApp serverless-express framework, specifically affecting versions 4.17.0 and 4.17.1. The vulnerability arises from improper validation and handling of the userId argument in the API Endpoint's TodoList.ts file, which is part of the example lambda function URL package. Attackers can remotely manipulate the userId parameter to gain unauthorized access to resources or perform actions reserved for other users, effectively bypassing authorization checks. This flaw does not require authentication or user interaction, making it easier to exploit remotely over the network. The vulnerability impacts confidentiality, integrity, and availability to a limited extent, as attackers can access or modify data they should not have permission for. Despite the public disclosure and vendor notification, no patches or vendor responses have been issued, and no active exploitation has been reported yet. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P) reflects a medium severity rating, highlighting the ease of remote exploitation with low attack complexity but requiring some privileges (PR:L).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Mar 2026, 00:41 UTC

Technical details

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