CVE-2023-34104

Regex Injection via Doctype Entities

HIGH
7.5
CVSS Score
Published: June 6, 2023 at 05:35 PM UTC
Updated: June 17, 2026 at 06:02 AM UTC
1 product affected across 1 vendorFast XML Parser

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Severity
HIGH7.5
Exploit prediction
EPSS 1%

Description

fast-xml-parser is an open source, pure javascript xml parser. fast-xml-parser allows special characters in entity names, which are not escaped or sanitized. Since the entity name is used for creating a regex for searching and replacing entities in the XML body, an attacker can abuse it for denial of service (DoS) attacks. By crafting an entity name that results in an intentionally bad performing regex and utilizing it in the entity replacement step of the parser, this can cause the parser to stall for an indefinite amount of time. This problem has been resolved in v4.2.4. Users are advised to upgrade. Users unable to upgrade should avoid using DOCTYPE parsing by setting the `processEntities: false` option.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 4.2.4
Affected range stops below 4.2.4, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-400CWE-1333

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