CVE-2026-26278
highpriority · track · 0EPSS 0.009 · 61 %ileDEEUUSEPSS · scored 2026-10-27
fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by `processEntities: false` option.
remediations
Vendor fix, mitigation, or workaround guidance, as published by each source.
A vendor fix is available.
- Fixedheroic-games-launcher-0:2.20.0-1.1.aarch64 as component of openSUSE Tumbleweedsuse_csaf
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
- Fixedheroic-games-launcher-0:2.20.0-1.1.ppc64le as component of openSUSE Tumbleweedsuse_csaf
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
- Fixedheroic-games-launcher-0:2.20.0-1.1.s390x as component of openSUSE Tumbleweedsuse_csaf
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
- Fixedheroic-games-launcher-0:2.20.0-1.1.x86_64 as component of openSUSE Tumbleweedsuse_csaf
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
- FixedSentio Creatorsick_psirt
It is strongly recommended to upgrade the Device Manger Extension to version 1.1.1.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (26)
Products and version ranges known to be affected.
- IBM App Connect Enterprise 12.0.1.0-12.0.12.25all versionscert_bundDEcpe:/a:ibm:app_connect_enterprise:12.0.1.0_-_12.0.12.25
- IBM App Connect Enterprise 13.0.1.0-13.0.7.1all versionscert_bundDEcpe:/a:ibm:app_connect_enterprise:13.0.1.0_-_13.0.7.1
- naturalintelligence fast-xml-parser4.1.3 → 5.3.6nvdUScpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*
advisories (5)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-0772IBM App Connect Enterprise (fast-xml-parser): Mehrere SchwachstellenDeutsch2026-03-17csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in IBM App Connect Enterprise ausnutzen, um einen Denial-of-Service-Zustand herbeizuführen oder Sicherheitsmaßnahmen zu umgehen, wodurch Cross-Site-Scripting-Angriffe ermöglicht werden.
- WID-SEC-W-2026-1220IBM App Connect Enterprise: Mehrere SchwachstellenDeutsch2026-04-21csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in IBM App Connect Enterprise ausnutzen, um Dateien zu manipulieren, und um einen Denial of Service Angriff durchzuführen.
- openSUSE-SU-2026:10236-1heroic-games-launcher-2.20.0-1.1 on GA media2026-02-23csaf · suse_csafDE
heroic-games-launcher-2.20.0-1.1 on GA media
- sca-2026-0014Fast-xml-parser vulnerabilities affect Sentio Creator Extension 'Device Manager'2026-10-14csaf · sick_psirtDE
Multiple vulnerabilities in the third-party component fast-xml-parser affect the Device Manager Extension in Sentio Creator. The extension is maintained and updated independently from SICK Sentio Creator, but successful exploitation of these vulnerabilities could impact the security of the Sentio Creator. SICK strongly recommends upgrading the extension to remediate the identified issues.
- GHSA-jmr7-xgp7-cmfjfast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)2026-02-17ghsa · osvUS
### Summary The XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. ### Details There is a check in `DocTypeReader.js` that tries to prevent entity expansion attacks by rejecting entities that reference other entities (it looks for & inside entity values). This does stop classic “Billion Laughs” payloads. However, it doesn’t stop a much simpler variant. If you define one large entity that contains only raw text (no & characters) and then reference it many times, the parser will happily expand it every time. There is no limit on how large the expanded result can become, or how many replacements are allowed. The problem is in `replaceEntitiesValue()` inside `OrderedObjParser.js`. It repeatedly runs `val.replace()` in a loop, without any checks on total output size or execution cost. As the entity grows or the number of references increases, parsing time explodes. Relevant code: `DocTypeReader.js` (lines 28–33): entity registration only checks for & `OrderedObjParser.js` (lines 439–458): entity replacement loop with no limits ### PoC ```js const { XMLParser } = require('fast-xml-parser'); const entity = 'A'.repeat(1000); const refs = '&big;'.repeat(100); const xml = `<!DOCTYPE foo [<!ENTITY big "${entity}">]><root>${refs}</root>`; console.time('parse'); new XMLParser().parse(xml); // ~4–8 seconds for ~1.3 KB of XML console.timeEnd('parse'); // 5,000 chars × 100 refs takes 200+ seconds // 50,000 chars × 1,000 refs will hang indefinitely ``` ### Impact This is a straightforward denial-of-service issue. Any service that parses user-supplied XML using the default configuration is vulnerable. Since Node.js runs on a single thread, the moment the parser starts expanding entities, the event loop is blocked. While this is happening, the server can’t handle any other requests. In testing, a payload of only a few kilobytes was enough to make a simple HTTP server completely unresponsive for several minutes, with all other requests timing out. ### Workaround Avoid using DOCTYPE parsing by `processEntities: false` option.
also known as (3)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (21)
External citations — patches, advisories, analysis.
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77cnnvd
- https://github.com/NaturalIntelligence/fast-xml-parser/releasesPatchcnnvd
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6cnnvd
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfjcnnvd
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77enisa_euvd
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6enisa_euvd
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfjenisa_euvd
- https://access.redhat.com/errata/RHSA-2026:40984nvd
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