CVE-2026-33349
Description
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
fast-xml-parsernpm | >= 4.0.0-beta.3, < 4.5.5 | 4.5.5 |
fast-xml-parsernpm | >= 5.0.0, < 5.5.7 | 5.5.7 |
Affected products
40cpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*+ 7 more
- cpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*range: >=4.0.1,<4.5.5
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:-:*:*:*:*:*:*
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta3:*:*:*:*:*:*
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta4:*:*:*:*:*:*
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta5:*:*:*:*:*:*
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta6:*:*:*:*:*:*
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta7:*:*:*:*:*:*
- cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0:beta8:*:*:*:*:*:*
- osv-coords31 versionspkg:apk/chainguard/dbgatepkg:apk/chainguard/kibana-8.19pkg:apk/chainguard/kibana-8.19-bitnamipkg:apk/chainguard/kibana-8.19-iamguardedpkg:apk/chainguard/kibana-9.0pkg:apk/chainguard/kibana-9.0-bitnamipkg:apk/chainguard/kibana-9.0-iamguardedpkg:apk/chainguard/kibana-9.1pkg:apk/chainguard/kibana-9.1-iamguardedpkg:apk/chainguard/kubeflow-pipelines-frontendpkg:apk/chainguard/langfuse-2-workerpkg:apk/chainguard/langfuse-3pkg:apk/chainguard/langfuse-3-workerpkg:apk/chainguard/langfuse-fips-2-workerpkg:apk/chainguard/langfuse-fips-3pkg:apk/chainguard/langfuse-fips-3-workerpkg:apk/chainguard/librechatpkg:apk/chainguard/opensearch-dashboards-3-fipspkg:apk/chainguard/prismpkg:apk/chainguard/renovatepkg:apk/chainguard/safpkg:apk/chainguard/tileserver-glpkg:apk/chainguard/tileserver-gl-fipspkg:apk/wolfi/kubeflow-pipelines-frontendpkg:apk/wolfi/langfuse-3pkg:apk/wolfi/langfuse-3-workerpkg:apk/wolfi/prismpkg:apk/wolfi/renovatepkg:apk/wolfi/safpkg:apk/wolfi/tileserver-glpkg:npm/fast-xml-parser
< 7.1.5-r0+ 30 more
- (no CPE)range: < 7.1.5-r0
- (no CPE)range: < 8.19.13-r4
- (no CPE)range: < 8.19.13-r4
- (no CPE)range: < 8.19.13-r4
- (no CPE)range: < 9.0.8-r15
- (no CPE)range: < 9.0.8-r15
- (no CPE)range: < 9.0.8-r15
- (no CPE)range: < 9.1.10-r8
- (no CPE)range: < 9.1.10-r8
- (no CPE)range: < 2.16.0-r10
- (no CPE)range: < 2.95.12-r16
- (no CPE)range: < 3.162.0-r1
- (no CPE)range: < 3.163.0-r0
- (no CPE)range: < 2.95.12-r19
- (no CPE)range: < 3.162.0-r0
- (no CPE)range: < 3.162.0-r1
- (no CPE)range: < 0.8.4-r3
- (no CPE)range: < 3.5.0-r8
- (no CPE)range: < 5.14.3-r13
- (no CPE)range: < 43.84.0-r1
- (no CPE)range: < 1.6.0-r0
- (no CPE)range: < 5.5.0-r11
- (no CPE)range: < 5.5.0-r11
- (no CPE)range: < 2.16.0-r10
- (no CPE)range: < 3.162.0-r1
- (no CPE)range: < 3.163.0-r0
- (no CPE)range: < 5.14.3-r13
- (no CPE)range: < 43.84.0-r1
- (no CPE)range: < 1.6.0-r0
- (no CPE)range: < 5.5.0-r11
- (no CPE)range: >= 4.0.0-beta.3, < 4.5.5
- Range: >= 4.0.0-beta.3, < 5.5.7
Patches
Vulnerability mechanics
References
5- github.com/NaturalIntelligence/fast-xml-parser/commit/239b64aa1fc5c5455ddebbbb54a187eb68c9fdb7nvdPatchWEB
- github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jp2q-39xq-3w4gnvdExploitMitigationVendor AdvisoryWEB
- github.com/advisories/GHSA-jp2q-39xq-3w4gghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-33349ghsaADVISORY
- github.com/NaturalIntelligence/fast-xml-parser/commit/88d0936a23dabe51bfbf42255e2ce912dfee2221ghsaWEB
News mentions
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