SB20260420117 - Multiple vulnerabilities in fast-xml-parser
Published: April 20, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 2 vulnerabilities.
1) XML Entity Expansion (CVE-ID: CVE-2026-33036)
CWE-ID: CWE-776 - Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper restriction of entity expansion in replaceEntitiesValue() in src/xmlparser/OrderedObjParser.js when parsing XML input containing numeric character references or standard XML entities. A remote attacker can send specially crafted XML input with massive numbers of numeric entity references to cause a denial of service.
The configured entity expansion limits are enforced only for DOCTYPE-defined entities, while numeric character references and standard XML entities are processed through a separate code path without expansion counting.
2) Improper Validation of Specified Quantity in Input (CVE-ID: CVE-2026-33349)
CWE-ID: CWE-1284 - Improper Validation of Specified Quantity in Input
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper validation of specified quantity in input in DocTypeReader when parsing XML input with entity processing limits set to 0. A remote attacker can supply a specially crafted XML document with many large entity definitions to cause a denial of service.
Only applications that explicitly set maxEntityCount or maxEntitySize to 0 are affected. The default configuration is not affected, and configurations with entity processing disabled are not affected.
Remediation
Install update from vendor's website.