CVE-2026-33349fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks.
Updated under an hour ago ()
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It affects naturalintelligence fast-xml-parser. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 5.9 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-1284
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
naturalintelligence fast-xml-parser naturalintelligence:fast-xml-parser | from 4.0.1 before 4.5.5; from 5.0.0 before 5.5.7; 4.0.0; 4.0.0; 4.0.0; 4.0.0; 4.0.0; 4.0.0; and 1 more ranges | NVD |
References
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/239b64aa1fc5c5455ddebbbb54a187eb68c9fdb7patch
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jp2q-39xq-3w4gexploit, mitigation, vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.