CVE-2026-110726 in Connected Services Platform
Summary
by MITRE • 10/15/2026
In `api-gateway` versions till `1.7.3`, The default rate-limit key resolver, `ClientIpKeyResolver`, derives the per-client bucket key from the leftmost element of the `X-Forwarded-For` request header. That element is supplied by the originating HTTP client and is not validated against any trusted-proxy list. A single attacker can therefore obtain an unlimited number of independent rate-limit buckets — one per unique header value — and completely bypass the gateway's request-rate limiting on every route that uses the shipped default configuration.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability in api-gateway versions up to 1.7.3 represents a critical failure in input validation within the rate-limiting subsystem, specifically affecting the ClientIpKeyResolver component. This resolver is responsible for determining the unique identifier used to track request counts per client, thereby enforcing throttling policies designed to prevent abuse and ensure service availability. The core technical flaw lies in the mechanism by which this identifier is derived: it extracts the leftmost element from the X-Forwarded-For HTTP header without performing any validation against a trusted proxy list or verifying the authenticity of the source IP address. In standard network architectures, the X-Forwarded-For header is intended to be appended by intermediate proxies that sit between the client and the server, preserving the original client's identity as the rightmost entry while adding their own addresses to the left. However, because this implementation trusts the first element provided directly by the originating HTTP client, it fails to distinguish between legitimate proxy-generated headers and maliciously crafted ones sent directly from an external attacker.
This architectural oversight allows a single attacker to bypass rate-limiting controls entirely through header manipulation. By simply changing the value of the X-Forwarded-For header in each subsequent request, the attacker can generate a unique leftmost IP address for every connection attempt. Since the resolver treats this unvalidated first element as the definitive client identifier, it creates a new, isolated rate-limit bucket for each distinct header value rather than aggregating requests under a single true source identity. Consequently, the gateway perceives these rapid-fire requests as coming from thousands of different clients, effectively granting the attacker an unlimited number of independent buckets. This results in a complete circumvention of request-rate limiting on every route that utilizes the shipped default configuration, undermining the security posture intended to protect backend services from volumetric attacks and resource exhaustion.
The operational impact of this vulnerability is severe, particularly for systems relying on api-gateway as a primary defense layer against denial-of-service conditions or brute-force authentication attempts. Attackers can exploit this flaw to conduct distributed-like attacks while appearing as single-source traffic, overwhelming downstream microservices with excessive load that the gateway fails to throttle appropriately. This not only degrades service performance and availability for legitimate users but also exposes backend systems to increased risk of exploitation through automated credential stuffing or API abuse. The lack of validation against a trusted proxy list means that even if the gateway is deployed behind reverse proxies, the security boundary remains porous because the initial trust anchor—the client-supplied header—is inherently untrustworthy in this context.
To mitigate this vulnerability, organizations must upgrade to api-gateway versions later than 1.7.3 where the issue has been addressed through stricter validation logic. In the interim, administrators should configure a trusted proxy list and ensure that the rate-limit key resolver is set to validate incoming X-Forwarded-For headers against this whitelist, ensuring only addresses from known infrastructure components are considered for IP extraction. Alternatively, switching to a different key resolution strategy that relies on more robust identifiers such as TLS client certificates or authenticated session tokens can eliminate reliance on easily spoofable HTTP headers entirely. This aligns with industry standards regarding input validation and secure configuration practices, specifically addressing CWE-20 Improper Input Validation and mitigating the risk associated with ATT&CK technique T1653 which involves misuse of trust relationships in network communications to evade detection or controls.