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🛡️ CVE-2026-44665 — fast-xml-builder

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-611 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes

# Summary

When an input data has quotes in attribute values but process entities is not enabled, it breaks the attribute value into multiple attributes. This gives the room for an attacker to insert unwanted attributes to the XML/HTML.

Detail

Malicious Input

```

{

a: {

"@_attr": '" onClick="alert(1)'

}

}

```

Output

```xml

<a attr="" onClick="alert(1)"></a>

```

Workarounds

If you're not ignoring attributes then keep processEntities flag true.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality low, integrity low, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: Required — someone has to click, open or visit something.
  • Scope: Changed — a successful attack reaches components beyond the vulnerable one.
  • Confidentiality impact: Low — limited, and the attacker does not choose what is affected.
  • Integrity impact: Low — limited, and the attacker does not choose what is affected.
  • Availability impact: None.

Weakness class

CVE-2026-44665 is classified as CWE-611: XML External Entity Reference (XXE). An XML parser resolves external entities, letting a crafted document read local files or reach internal services.

Affected software

CVE-2026-44665 is recorded against 2 packages.

  • fast-xml-builder
  • unknown

Timeline and source

Published on 8 May 2026 and last revised on 14 May 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Package)

Other advisories for this package

fast-xml-builder has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-611: XML External Entity Reference (XXE)) in other software:

CVE-2026-44665 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CWE CWE-611
Public Exploit ✅ No
Source NVD
Published 2026-05-08
Updated 2026-08-20
Modified 2026-05-14
Fix URL N/A

Affected Packages

Software From version Fixed in
fast-xml-builder — —
unknown — —

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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