CVE-2026-33349 | NaturalIntelligence fast-xml-parser up to 5.5.6 improper validation of specified quantity in input

VDB-352864 · CVE-2026-33349 · GCVE-0-2026-33349 NATURALINTELLIGENCE FAST-XML-PARSER UP TO 5.5.6 IMPROPER VALIDATION OF SPECIFIED QUANTITY IN INPUT HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 4.7 $0-$5k 3.19 Summaryinfo A vulnerability categorized as problematic has been discovered in NaturalIntelligence fast-xml-parser up to 5.5.6. The affected element is an unknown function. Executing a manipulation can lead to improper validation of specified quantity in input. The identification of this vulnerability is CVE-2026-33349. The attack may be launched remotely. There is no exploit available. It is advisable to upgrade the affected component. Detailsinfo A vulnerability classified as problematic was found in NaturalIntelligence fast-xml-parser up to 5.5.6. This vulnerability affects an unknown functionality. The manipulation with an unknown input leads to a improper validation of specified quantity in input vulnerability. The CWE definition for the vulnerability is CWE-1284. The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties. As an impact it is known to affect availability. CVE summarizes: 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. The advisory is shared for download at github.com. This vulnerability was named CVE-2026-33349 since 03/18/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. Upgrading to version 5.5.7 eliminates this vulnerability. Productinfo Vendor NaturalIntelligence Name fast-xml-parser Version 5.5.0 5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 5.5.6 Website Product: https://github.com/NaturalIntelligence/fast-xml-parser/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 4.8 VulDB Meta Temp Score: 4.7 VulDB Base Score: 3.7 VulDB Temp Score: 3.6 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 5.9 CNA Vector (GitHub_M): 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Improper validation of specified quantity in input CWE: CWE-1284 / CWE-703 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: fast-xml-parser 5.5.7 Timelineinfo 03/18/2026 CVE reserved 03/24/2026 +6 days Advisory disclosed 03/24/2026 +0 days VulDB entry created 03/24/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: github.com Status: Confirmed CVE: CVE-2026-33349 (🔒) GCVE (CVE): GCVE-0-2026-33349 GCVE (VulDB): GCVE-100-352864 Entryinfo Created: 03/24/2026 20:59 Changes: 03/24/2026 20:59 (62) Complete: 🔍 Cache ID: 99:819:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸