CVE-2026-33036
published 2026-03-20CVE-2026-33036: fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass…
PriorityP343high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.58%
44.1th percentile
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when developers have configured strict limits. This issue has been fixed in version 5.5.6.
Affected
5 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | node-webfont | — | — |
| naturalintelligence | fast-xml-parser | — | — |
| naturalintelligence | fast-xml-parser | >= 4.0.0-beta.3 < 4.5.5 | 4.5.5 |
| naturalintelligence | fast-xml-parser | >= 4.0.1 < 5.5.6 | 5.5.6 |
| naturalintelligence | fast-xml-parser | >= 5.0.0 < 5.5.6 | 5.5.6 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
ghsa7.5HIGH
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
Stop checking back — get the weekly exploitation signal.
Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
OSV
CVE-2026-33036: fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks
osv·2026-03-20·CVSS 7.5
CVE-2026-33036 [HIGH] CVE-2026-33036: fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when d
GHSA
fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
ghsa·2026-03-17·CVSS 7.5
CVE-2026-33036 [HIGH] CWE-776 fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
## Summary
The fix for CVE-2026-26278 added entity expansion limits (`maxTotalExpansions`, `maxExpandedLength`, `maxEntityCount`, `maxEntitySize`) to prevent XML entity expansion Denial of Service. However, these limits are only enforced for DOCTYPE-defined entities. **Numeric character references** (`&#NNN;` and `&#xHH;`) and standard XML entities (` `, etc.) are processed through a separate code path that does NOT enforce any expansion limits.
An attacker can use massive numbers of numeric entity references to completely bypass all configured limits, causing excessive memory allocation and CPU consumption.
## Affected Versions
fast-xml-parser v5.x through v5
OSV
fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
osv·2026-03-17·CVSS 7.5
CVE-2026-33036 [HIGH] fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
## Summary
The fix for CVE-2026-26278 added entity expansion limits (`maxTotalExpansions`, `maxExpandedLength`, `maxEntityCount`, `maxEntitySize`) to prevent XML entity expansion Denial of Service. However, these limits are only enforced for DOCTYPE-defined entities. **Numeric character references** (`&#NNN;` and `&#xHH;`) and standard XML entities (` `, etc.) are processed through a separate code path that does NOT enforce any expansion limits.
An attacker can use massive numbers of numeric entity references to completely bypass all configured limits, causing excessive memory allocation and CPU consumption.
## Affected Versions
fast-xml-parser v5.x through v5
Red Hat
fast-xml-parser: fast-xml-parser: Denial of Service via XML entity expansion bypass
vendor_redhat·2026-03-20·CVSS 7.5
CVE-2026-33036 [HIGH] CWE-776 fast-xml-parser: fast-xml-parser: Denial of Service via XML entity expansion bypass
fast-xml-parser: fast-xml-parser: Denial of Service via XML entity expansion bypass
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB o
Debian
CVE-2026-33036: node-webfont - fast-xml-parser allows users to process XML from JS object without C/C++ based l...
vendor_debian·2026·CVSS 7.5
CVE-2026-33036 [HIGH] CVE-2026-33036: node-webfont - fast-xml-parser allows users to process XML from JS object without C/C++ based l...
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when d
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-33036 fast-xml-parser: fast-xml-parser: Denial of Service via XML entity expansion bypass
bugzilla·2026-03-20·CVSS 7.5
CVE-2026-33036 [HIGH] CVE-2026-33036 fast-xml-parser: fast-xml-parser: Denial of Service via XML entity expansion bypass
CVE-2026-33036 fast-xml-parser: fast-xml-parser: Denial of Service via XML entity expansion bypass
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can
Bugzilla
CVE-2026-33036 h3: fast-xml-parser: Denial of Service via XML entity expansion bypass [fedora-42]
bugzilla·2026-03-20·CVSS 7.5
CVE-2026-33036 [HIGH] CVE-2026-33036 h3: fast-xml-parser: Denial of Service via XML entity expansion bypass [fedora-42]
CVE-2026-33036 h3: fast-xml-parser: Denial of Service via XML entity expansion bypass [fedora-42]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Discussion:
This message is a reminder that Fedora Linux 42 is nearing its end of life.
Fedora will stop maintaining and issuing updates for Fedora Linux 42 on 2026-05-13.
It is Fedora's policy to close all bug reports from releases that are no longer
maintained. At that time this bug will be closed as EOL if it remains open with a
'version' of '42'.
Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version,
Wiz
CVE-2026-33036 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-33036 [HIGH] CVE-2026-33036 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-33036 :
JavaScript vulnerability analysis and mitigation
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory alloc
2026-03-20
Published