From c1a09b951fd779f2967fe84938de2e194303d7c8 Mon Sep 17 00:00:00 2001
From: "renovate[bot]" <29139614+renovate[bot]@users.noreply.github.com>
Date: Wed, 18 Mar 2026 13:28:53 +0800
Subject: [PATCH] chore: bump up fast-xml-parser version to v5.5.6 [SECURITY]
(#14676)
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This PR contains the following updates:
| Package | Change |
[Age](https://docs.renovatebot.com/merge-confidence/) |
[Confidence](https://docs.renovatebot.com/merge-confidence/) |
|---|---|---|---|
|
[fast-xml-parser](https://redirect.github.com/NaturalIntelligence/fast-xml-parser)
| [`5.4.1` →
`5.5.6`](https://renovatebot.com/diffs/npm/fast-xml-parser/5.4.1/5.5.6)
|

|

|
### GitHub Vulnerability Alerts
####
[CVE-2026-33036](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r)
## 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 `HH;`) 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 v5.5.3 (and likely v5.5.5 on npm)
## Root Cause
In `src/xmlparser/OrderedObjParser.js`, the `replaceEntitiesValue()`
function has two separate entity replacement loops:
1. **Lines 638-670**: DOCTYPE entities — expansion counting with
`entityExpansionCount` and `currentExpandedLength` tracking. This was
the CVE-2026-26278 fix.
2. **Lines 674-677**: `lastEntities` loop — replaces standard entities
including `num_dec` (`/([0-9]{1,7});/g`) and `num_hex`
(`/([0-9a-fA-F]{1,6});/g`). **This loop has NO expansion counting at
all.**
The numeric entity regex replacements at lines 97-98 are part of
`lastEntities` and go through the uncounted loop, completely bypassing
the CVE-2026-26278 fix.
## Proof of Concept
```javascript
const { XMLParser } = require('fast-xml-parser');
// Even with strict explicit limits, numeric entities bypass them
const parser = new XMLParser({
processEntities: {
enabled: true,
maxTotalExpansions: 10,
maxExpandedLength: 100,
maxEntityCount: 1,
maxEntitySize: 10
}
});
// 100K numeric entity references — should be blocked by maxTotalExpansions=10
const xml = `${'65;'.repeat(100000)}`;
const result = parser.parse(xml);
// Output: 500,000 chars — bypasses maxExpandedLength=100 completely
console.log('Output length:', result.root.length); // 500000
console.log('Expected max:', 100); // limit was 100
```
**Results:**
- 100K `65;` references → 500,000 char output (5x default
maxExpandedLength of 100,000)
- 1M references → 5,000,000 char output, ~147MB memory consumed
- Even with `maxTotalExpansions=10` and `maxExpandedLength=100`, 10K
references produce 50,000 chars
- Hex entities (`A`) exhibit the same bypass
## Impact
**Denial of Service** — An attacker who can provide XML input to
applications using fast-xml-parser can cause:
- Excessive memory allocation (147MB+ for 1M entity references)
- CPU consumption during regex replacement
- Potential process crash via OOM
This is particularly dangerous because the application developer may
have explicitly configured strict entity expansion limits believing they
are protected, while numeric entities silently bypass all of them.
## Suggested Fix
Apply the same `entityExpansionCount` and `currentExpandedLength`
tracking to the `lastEntities` loop (lines 674-677) and the HTML
entities loop (lines 680-686), similar to how DOCTYPE entities are
tracked at lines 638-670.
## Workaround
Set `htmlEntities:false`
---
### Release Notes
NaturalIntelligence/fast-xml-parser (fast-xml-parser)
###
[`v5.5.6`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/e54155f53048e9d58e27f170d3ccff15176b6671...870043e75e78545192bc70950c6286d36c7cdf23)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.5...v5.5.6)
###
[`v5.5.5`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/ea07bb2e8435a88136c0e46d7ee8a345107b7582...e54155f53048e9d58e27f170d3ccff15176b6671)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.4...v5.5.5)
###
[`v5.5.4`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.3...ea07bb2e8435a88136c0e46d7ee8a345107b7582)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.3...v5.5.4)
###
[`v5.5.3`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.2...v5.5.3)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.2...v5.5.3)
###
[`v5.5.2`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.1...e0a14f7d15a293732e630ce1b7faa39924de2359)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.1...v5.5.2)
###
[`v5.5.1`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.1):
integrate path-expression-matcher
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.5.0...v5.5.1)
- support path-expression-matcher
- fix: stopNode should not be parsed
- performance improvement for stopNode checking
###
[`v5.5.0`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.4.2...ce017923460f92861e8fc94c91e52f9f5bd6a1b0)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.4.2...v5.5.0)
###
[`v5.4.2`](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.4.1...v5.4.2)
[Compare
Source](https://redirect.github.com/NaturalIntelligence/fast-xml-parser/compare/v5.4.1...v5.4.2)
---
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---
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---
yarn.lock | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/yarn.lock b/yarn.lock
index a4cfcb574e..28e1ca9c8f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -23442,22 +23442,25 @@ __metadata:
languageName: node
linkType: hard
-"fast-xml-builder@npm:^1.0.0":
- version: 1.0.0
- resolution: "fast-xml-builder@npm:1.0.0"
- checksum: 10/06c04d80545e5c9f4d1d6cca00567b5cc09953a92c6328fa48cfb4d7f42630313b8c2bb62e9cb81accee7bb5e1c5312fcae06c3d20dbe52d969a5938233316da
+"fast-xml-builder@npm:^1.1.4":
+ version: 1.1.4
+ resolution: "fast-xml-builder@npm:1.1.4"
+ dependencies:
+ path-expression-matcher: "npm:^1.1.3"
+ checksum: 10/32937866aaf5a90e69d1f4ee6e15e875248d5b5d2afd70277e9e8323074de4980cef24575a591b8e43c29f405d5f12377b3bad3842dc412b0c5c17a3eaee4b6b
languageName: node
linkType: hard
"fast-xml-parser@npm:^5.3.4":
- version: 5.4.1
- resolution: "fast-xml-parser@npm:5.4.1"
+ version: 5.5.6
+ resolution: "fast-xml-parser@npm:5.5.6"
dependencies:
- fast-xml-builder: "npm:^1.0.0"
+ fast-xml-builder: "npm:^1.1.4"
+ path-expression-matcher: "npm:^1.1.3"
strnum: "npm:^2.1.2"
bin:
fxparser: src/cli/cli.js
- checksum: 10/2b40067c3ad3542ca197d1353bcb0416cd5db20d5c66d74ac176b99af6ff9bd55a6182d36856a2fd477c95b8fc1f07405475f1662a31185480130ba7076c702a
+ checksum: 10/91a42a0cf99c83b0e721ceef9c189509e96c91c1875901c6ce6017f78ad25284f646a77a541e96ee45a15c2f13b7780d090c906c3ec3f262db03e7feb1e62315
languageName: node
linkType: hard
@@ -30280,6 +30283,13 @@ __metadata:
languageName: node
linkType: hard
+"path-expression-matcher@npm:^1.1.3":
+ version: 1.1.3
+ resolution: "path-expression-matcher@npm:1.1.3"
+ checksum: 10/9a607d0bf9807cf86b0a29fb4263f0c00285c13bedafb6ad3efc8bc87ae878da2faf657a9138ac918726cb19f147235a0ca695aec3e4ea1ee04641b6520e6c9e
+ languageName: node
+ linkType: hard
+
"path-is-absolute@npm:^1.0.0":
version: 1.0.1
resolution: "path-is-absolute@npm:1.0.1"