fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. From version 4.0.0-beta.3 to before version 5.5.7, the DocTypeReader in fast-xml-parser uses JavaScript truthy checks to evaluate maxEntityCount and maxEntitySize configuration limits. When a developer explicitly sets either limit to 0 — intending to disallow all entities or restrict entity size to zero bytes — the falsy nature of 0 in JavaScript causes the guard conditions to short-circuit, completely bypassing the limits.
An attacker who can supply XML input to such an application can trigger unbounded entity expansion, leading to memory exhaustion and denial of service. This issue has been patched in version 5.5.7.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products 9
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*
|
4.0.1
|
4.5.5
|
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*
|
5.0.0
|
5.5.7
|
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:-:*:*:*:*:*:*
|
— | — |
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta3:*:*:*:*:*:*
|
— | — |
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta4:*:*:*:*:*:*
|
— | — |
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta5:*:*:*:*:*:*
|
— | — |
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta6:*:*:*:*:*:*
|
— | — |
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta7:*:*:*:*:*:*
|
— | — |
|
Naturalintelligence Fast-Xml-Parser
cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta8:*:*:*:*:*:*
|
— | — |