CVE-2023-26920
fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
6.5
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
- Record
CVE-2023-26920- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-1321
- Updated
- 2026-11-02
CVE List No score
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
- Record
CVE-2023-26920- Updated
- 2026-11-02
EUVDEUVD-2023-1910 No score
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
- Record
EUVD-2023-1910- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-x3cc-x39p-42qx
6.5
fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name
Impact
As a part of this vulnerability, user was able to se code using __proto__ as a tag or attribute name.
const { XMLParser, XMLBuilder, XMLValidator} = require("fast-xml-parser");
let XMLdata = "<__proto__><polluted>hacked</polluted></__proto__>"
const parser = new XMLParser();
let jObj = parser.parse(XMLdata);
console.log(jObj.polluted) // should return hacked
Patches
The problem has been patched in v4.1.2
Workarounds
User can check for "proto" in the XML string before parsing it to the parser.
References
https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7
- Record
GHSA-x3cc-x39p-42qx- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-1321
- Updated
- 2026-11-02
OSVCVE-2021-26920
6.5
In the Druid ingestion system, the InputSource is used for reading data from a certain data source. However, the HTTP InputSource allows authenticated users to read data from other sources than intended, such as the local file system, with the privileges of the Druid server process. This is not an elevation of privilege when users access Druid directly, since Druid also provides the Local InputSource, which allows the same level of access. But it is problematic when users interact with Druid indirectly through an application that allows users to specify the HTTP InputSource, but not the Local InputSource. In this case, users could bypass the application-level restriction by passing a file URL to the HTTP InputSource.
- Record
CVE-2021-26920- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVDEBIAN-CVE-2023-26920
6.5
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
- Record
DEBIAN-CVE-2023-26920- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
Show 8 moreShow less
OSVGHSA-793h-6f7r-6qvm
6.5
Druid ingestion system Authenticated users can read data from other sources than intended
In the Druid ingestion system, the InputSource is used for reading data from a certain data source. However, the HTTP InputSource allows authenticated users to read data from other sources than intended, such as the local file system, with the privileges of the Druid server process. This is not an elevation of privilege when users access Druid directly, since Druid also provides the Local InputSource, which allows the same level of access. But it is problematic when users interact with Druid indirectly through an application that allows users to specify the HTTP InputSource, but not the Local InputSource. In this case, users could bypass the application-level restriction by passing a file URL to the HTTP InputSource.
- Record
GHSA-793h-6f7r-6qvm- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-863
- Updated
- 2026-11-02
OSVGHSA-x3cc-x39p-42qx
6.5
fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name
Impact
As a part of this vulnerability, user was able to se code using __proto__ as a tag or attribute name.
const { XMLParser, XMLBuilder, XMLValidator} = require("fast-xml-parser");
let XMLdata = "<__proto__><polluted>hacked</polluted></__proto__>"
const parser = new XMLParser();
let jObj = parser.parse(XMLdata);
console.log(jObj.polluted) // should return hacked
Patches
The problem has been patched in v4.1.2
Workarounds
User can check for "proto" in the XML string before parsing it to the parser.
References
https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7
- Record
GHSA-x3cc-x39p-42qx- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-1321
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2023-26920
6.5
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
- Record
UBUNTU-CVE-2023-26920- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVCLSA-2026-1781744123 No score
TuxCare security update for fast-xml-parser (2 CVEs)
TuxCare rebuilt fast-xml-parser to address 2 CVEs. Fixed in 3.19.0-tuxcare.1.
- Record
CLSA-2026-1781744123- Updated
- 2026-11-02
OSVCLSA-2026-1781744124 No score
TuxCare security update for fast-xml-parser (2 CVEs)
TuxCare rebuilt fast-xml-parser to address 2 CVEs. Fixed in 3.17.5-tuxcare.1.
- Record
CLSA-2026-1781744124- Updated
- 2026-11-02
OSVCLSA-2026-1781744131 No score
TuxCare security update for fast-xml-parser (2 CVEs)
TuxCare rebuilt fast-xml-parser to address 2 CVEs. Fixed in 3.14.0-tuxcare.1.
- Record
CLSA-2026-1781744131- Updated
- 2026-11-02
OSV No score
fast-xml-parser before 4.1.2 allows proto for Prototype Pollution.
- Record
CVE-2023-26920- Updated
- 2026-11-02
OSVROOT-APP-NPM-CVE-2023-26920 No score
CVE-2023-26920 in @rootio/fast-xml-parser - Patched by Root
Root has patched CVE-2023-26920 in the @rootio/fast-xml-parser package for Root:npm. Multiple fixed versions available.
- Record
ROOT-APP-NPM-CVE-2023-26920- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
fast-xml-parsernpm |
before 4.1.2 | 4.1.2 |
fast-xml-parserTuxCare:npm From an advisory covering 2 CVEs |
3.19.0-tuxcare.0 up to 3.19.0-tuxcare.1, plus listed versions 3.19.0 |
3.19.0-tuxcare.1 |
fast-xml-parserTuxCare:npm From an advisory covering 2 CVEs |
3.17.5-tuxcare.0 up to 3.17.5-tuxcare.1, plus listed versions 3.17.5 |
3.17.5-tuxcare.1 |
fast-xml-parserTuxCare:npm From an advisory covering 2 CVEs |
3.14.0-tuxcare.0 up to 3.14.0-tuxcare.1, plus listed versions 3.14.0 |
3.14.0-tuxcare.1 |
node-webfontDebian:12 |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-1011.4.0+dfsg2+~cs35.7.26-1111.4.0+dfsg2+~cs35.7.26-1211.4.0+dfsg2+~cs35.7.26-1311.4.0+dfsg2+~cs35.7.26-14 Show 10 moreShow less11.4.0+dfsg2+~cs35.7.26-1511.4.0+dfsg2+~cs35.7.26-1611.4.0+dfsg2+~cs35.7.26-1811.4.0+dfsg2+~cs35.7.26-1911.4.0+dfsg2+~cs35.7.26-2011.4.0+dfsg2+~cs35.7.26-2111.4.0+dfsg2+~cs35.7.26-2211.4.0+dfsg2+~cs35.7.26-711.4.0+dfsg2+~cs35.7.26-811.4.0+dfsg2+~cs35.7.26-9 |
None known |
node-webfontDebian:13 |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-1311.4.0+dfsg2+~cs35.7.26-1411.4.0+dfsg2+~cs35.7.26-1511.4.0+dfsg2+~cs35.7.26-1611.4.0+dfsg2+~cs35.7.26-18 Show 4 moreShow less11.4.0+dfsg2+~cs35.7.26-1911.4.0+dfsg2+~cs35.7.26-2011.4.0+dfsg2+~cs35.7.26-2111.4.0+dfsg2+~cs35.7.26-22 |
None known |
node-webfontDebian:14 |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-1311.4.0+dfsg2+~cs35.7.26-1411.4.0+dfsg2+~cs35.7.26-1511.4.0+dfsg2+~cs35.7.26-1611.4.0+dfsg2+~cs35.7.26-18 Show 4 moreShow less11.4.0+dfsg2+~cs35.7.26-1911.4.0+dfsg2+~cs35.7.26-2011.4.0+dfsg2+~cs35.7.26-2111.4.0+dfsg2+~cs35.7.26-22 |
None known |
org.apache.druid:druid-coreMaven From an advisory covering 2 CVEs |
before 0.21.0, plus listed versions 0.14.0-incubating0.14.1-incubating0.14.2-incubating0.15.0-incubating0.15.1-incubating Show 10 moreShow less0.16.0-incubating0.16.1-incubating0.17.00.17.10.18.00.18.10.19.00.20.00.20.10.20.2 |
0.21.0 |
fast-xml-parsernpm From an advisory covering 2 CVEs |
before 4.1.2 | 4.1.2 |
@rootio/fast-xml-parserRoot:npm |
before 3.21.1-root.io.1 | 3.21.1-root.io.1 |
Show 5 moreShow less
| Package | Affected | Fixed |
|---|---|---|
fast-xml-parserRoot:npm |
before 3.21.1-aikido.1 | 3.21.1-aikido.1 |
node-webfontUbuntu:24.04:LTS |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-7ubuntu1 |
None known |
node-webfontUbuntu:25.10 |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-1011.4.0+dfsg2+~cs35.7.26-13ubuntu2 |
None known |
node-webfontUbuntu:26.10 |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-1811.4.0+dfsg2+~cs35.7.26-19 |
None known |
node-webfontUbuntu:26.04:LTS |
All versions, plus listed versions 11.4.0+dfsg2+~cs35.7.26-13ubuntu211.4.0+dfsg2+~cs35.7.26-1411.4.0+dfsg2+~cs35.7.26-1511.4.0+dfsg2+~cs35.7.26-16build111.4.0+dfsg2+~cs35.7.26-18 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-26920 is a medium vulnerability (CVSS 6.5) in Naturalintelligence Fast Xml Parser, published July 2, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.15%, the 67th percentile. Fixed in fast-xml-parser 4.1.2.
References
gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7
github.com/advisories/GHSA-793h-6f7r-6qvm
github.com/NaturalIntelligence/fast-xml-parser/commit/2b032a4f799c63d83991e4f992f1c68e4dd05804
github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-x3cc-x39p-42qx
nvd.nist.gov/vuln/detail/CVE-2023-26920
github.com/advisories/GHSA-x3cc-x39p-42qx
Show 15 moreShow less
lists.apache.org/thread.html/r304dfe56a5dfe1b2d9166b24d2c74ad1c6730338b20aef77a00ed2be%40%3Cannounce.apache.org%3E
lists.apache.org/thread.html/r61aab724cf97d80da7f02d50e9af6de5c7c40dd92dab7518746fbaa2%40%3Cannounce.apache.org%3E
lists.apache.org/thread.html/rc9400a70d0ec5cdb8a3486fc5ddb0b5282961c0b63e764abfbcb9f5d%40%3Cdev.druid.apache.org%3E
openwall.com/lists/oss-security/2021/07/02/1
openwall.com/lists/oss-security/2021/09/24/1
lists.apache.org/thread.html/r29e45561343cc5cf7d3290ee0b0e94e565faab19c20d022df9b5e29c%40%3Cdev.druid.apache.org%3E
github.com/CVEProject/cvelistV5/tree/main/cves/2023/26xxx/CVE-2023-26920.json
security-tracker.debian.org/tracker/CVE-2023-26920
nvd.nist.gov/vuln/detail/CVE-2021-26920
lists.apache.org/thread.html/r304dfe56a5dfe1b2d9166b24d2c74ad1c6730338b20aef77a00ed2be@%3Cannounce.apache.org%3E
lists.apache.org/thread.html/r61aab724cf97d80da7f02d50e9af6de5c7c40dd92dab7518746fbaa2@%3Cannounce.apache.org%3E
lists.apache.org/thread.html/rc9400a70d0ec5cdb8a3486fc5ddb0b5282961c0b63e764abfbcb9f5d@%3Cdev.druid.apache.org%3E
github.com/NaturalIntelligence/fast-xml-parser
ubuntu.com/security/CVE-2023-26920
cve.org/CVERecord?id=CVE-2023-26920