API Connect: Improper Restriction of XML External Entity Reference
CVE-2026-16884 is a critical-severity improper restriction of XML external entity reference vulnerability in API Connect from IBM, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected API Connect versions: 12.1.0.0 through 12.1.1.2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.5% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of API Connect you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on ibm.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| IBM | API Connect | 12.1.0.0 through 12.1.1.2 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:L. Scored by CNA (us.ibm.com).
Official description
IBM API Connect 12.1.0.0 through 12.1.1.2 could allow a remote attacker to obtain sensitive information due to an XML external entity (XXE) injection.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of XML External Entity Reference
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
How developers prevent this class of flaw
- Many XML parsers and validators can be configured to disable external entity expansion.
More Improper Restriction of XML External Entity Reference vulnerabilities (CWE-611)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in API Connect
- 7.2 High severity
- 7.5 High severity
- 8.3 High severity
- 9.4 Critical severity
- 9.3 Critical severity
- 9.6 Critical severity
Recent Improper Restriction of XML External Entity Reference vulnerabilities
- 7.5 High severity
- 7.1 High severity
- 7.1 High severity
- 8.1 High severity
- 8.2 High severity
- 7.2 High severity
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