NL Portal Backend Libraries: Unauthenticated form resolver forwards the privileged Objecten-API token to a caller-supplied URL (SSRF)

published 2026-06-19 4 mo ago modified 2026-10-16 23 d ago also GHSA-xm3x-9cfw-jhx4 , EUVD-2026-102226

cvss: 5.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits: 0; none known

NL Portal Backend Libraries provide backend components for Dutch government portals that interact with residents, customers, suppliers, and partner organizations. From 1.1.0 until 3.0.4, and in 3.1.0, the public getFormDefinitionByObjectenApiUrl and deprecated getFormDefinitionById GraphQL resolvers are reachable without CommonGroundAuthentication and forward a caller-influenced URL through ObjectenApiService.getObjectByUrl to ObjectsApiClient.getObjectByUrl, which attaches the privileged Objecten-API token. The host-equality check restricts requests to the configured Objecten-API host but does not constrain the scheme, port, or path, allowing an unauthenticated caller to induce a token-bearing request to a chosen endpoint on that host. Standard deployments are not exposed to cross-host SSRF, token capture requires attacker-controlled routing on the configured host, and typed deserialization limits returned data to objects shaped like form definitions. The 3.0 release line is fixed in version 3.0.4. The advisory does not identify a fixed 3.1 release.

Patch / fix

fixed in 1 links 3

maven nl.nl-portal:form 3.0.4

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: partial
Assessed: 24 d ago (2026-10-15)

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/nl-portal/nl-portal-backend-libraries/security/advisories/GHSA-xm3x-9cfw-jhx4 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
maven	nl.nl-portal:form	>=1.1.0, <3.0.4	3.0.4

Affected products

nl-portal nl-portal-backend-libraries

Classification

Weakness

CWE-862 Missing Authorization
CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary