Medium severity · published Dec 12, 2023
CVE-2023-26920
fast-xml-parser before 4.1.2 allows __proto__ for Prototype Pollution
6.5
CVSS
1.2%
EPSS
No
On KEV
Description
fast-xml-parser before 4.1.2 allows __proto__ for Prototype Pollution.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.2% · higher than 67% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FX
Fast Xml Parser · Naturalintelligence
before 4.1.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-26920
CVE.org
https://www.cve.org/CVERecord?id=CVE-2023-26920
Exploit
https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7
Patch
https://github.com/NaturalIntelligence/fast-xml-parser/commit/2b032a4f799c63d83991e4f992f1c68e4dd05804
Third Party Advisory
https://github.com/advisories/GHSA-793h-6f7r-6qvm
More from Fast Xml Parser
9.3
CVE-2026-25896
fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names
8.7
CVE-2026-73569
fast-xml-parser: Repeated DOCTYPE declarations reset entity expansion limits
7.5
CVE-2026-33036
fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
7.5
CVE-2026-27942
fast-xml-parser has stack overflow in XMLBuilder with preserveOrder
7.5
CVE-2026-26278
fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)