CVE-2026-126345VulnerabilityPublished 12 Nov 2026

basic-ftp: Uncaught TypeError

Affects basic-ftpSource GCVE Database

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Authoritative record:CVE-2026-126345· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 6.2.4 when convenient.

Data as of 12 Nov 2026, 22:23 UTC

CVSS 3.1 base score

5.3Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	5.3

Patch: Available – fixed in 6.2.4

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 12 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 12 Nov 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

Upgrade basic-ftp to 6.2.4.

Affected software

Product	Affected	Fixed in
npmbasic-ftp	Affected <6.2.4	Fixed in 6.2.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in basic-ftp version 6.2.4 that addresses this issue. Users should upgrade to version 6.2.4 or later. Until upgraded, applications should wrap all calls to Client.list() and related APIs in try/catch blocks to handle potential promise rejections and prevent process crashes. Avoid using basic-ftp over plaintext FTP connections or ensure directory listing inputs are sanitized if possible.

Description

basic-ftp versions prior to 6.2.4 contain a vulnerability in the MLSD directory-listing parser where an unvalidated fact name "__proto__" causes a TypeError. This error is not caught by the client's retry logic and results in an unhandled promise rejection that can crash the Node.js process. The issue arises because the parser uses a plain object literal keyed by untrusted server input, allowing prototype pollution-like behavior. Any FTP server or attacker on a plaintext FTP session can trigger this denial of service by sending a crafted directory listing line.

Impact

An attacker controlling an FTP server or able to intercept and modify FTP directory listings on a plaintext connection can cause the client application using basic-ftp to crash by sending a directory listing line containing the fact name "__proto__". This results in a denial of service due to an uncaught TypeError that propagates as a rejected promise and crashes the Node.js process if not properly handled. There is no direct confidentiality or integrity impact reported. The vulnerability affects availability of applications using basic-ftp versions before 6.2.4.

Summary

The MLSD directory-listing parser in basic-ftp (src/parseListMLSD.ts) uses a plain object literal factHandlersByName keyed by fact names from the FTP server response without validation. When the fact name "__proto__" is encountered, the lookup returns Object.prototype instead of undefined, bypassing the function existence check. The code then attempts to call Object.prototype as a function, throwing a TypeError. This error is not an FTPError and thus is not caught by Client.list()'s retry logic, causing the promise to reject and potentially crashing the Node.js process if unhandled. This affects all calls relying on Client.list(), including downloadToDir, uploadFromDir, clearWorkingDir, and removeDir. The root cause is unsafe use of an object literal as a dictionary for untrusted keys, leading to a denial of service via unhandled exceptions.

CWE-1321Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution) (opens in a new tab)
Variant weakness
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
Implementation
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
Architecture and Design
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
Implementation · Input Validation
When handling untrusted objects, validating using a schema can be used.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Exploiting Incorrectly Configured Access Control Security Levels (opens in a new tab)
Manipulating User-Controlled Variables (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-248Uncaught Exception (opens in a new tab)
Base weaknessOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
An exception is thrown from a function, but it is not caught.
Requirements
The choice between a language which has named or unnamed exceptions needs to be done. While unnamed exceptions exacerbate the chance of not properly dealing with an exception, named exceptions suffer from the up call version of the weak base class problem.
Requirements
A language can be used which requires, at compile time, to catch all serious exceptions. However, one must make sure to use the most current version of the API as new exceptions could be added.
Implementation
Catch all relevant exceptions. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2026, 22:23 UTC

WeaknessesCWE-1321, CWE-248

Technical details

References

Community reviews

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