API Connect: Unintended Proxy or Intermediary
CVE-2026-16920 is a critical-severity unintended proxy or intermediary 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 attacker with a low-privileged account, 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.
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
- LowA basic user account is enough.
- 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
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (us.ibm.com).
Official description
IBM API Connect 12.1.0.0 through 12.1.1.2 could allow a remote authenticated attacker to bypass security restrictions due to a confused deputy vulnerability.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Unintended Proxy or Intermediary
The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere.
How developers prevent this class of flaw
- Enforce the use of strong mutual authentication mechanism between the two parties.
- Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.
More Unintended Proxy or Intermediary vulnerabilities (CWE-441)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- 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 Unintended Proxy or Intermediary vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
- 8.4 High severity
- 8.4 High severity
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