In the fast-evolving world of AI, security flaws can turn helpful tools into gateways for serious breaches.
A recent discovery highlights a server-side request forgery (SSRF) vulnerability in ChatGPT’s “Actions” feature, which affects custom GPTs in OpenAI’s popular chatbot.
This flaw allows attackers to trick the system into accessing internal cloud resources, potentially exposing sensitive credentials.
Security researcher SirLeeroyJenkins uncovered this issue while casually experimenting with custom assistants, demonstrating how even innovative features can introduce overlooked risks.
The vulnerability stems from the way custom GPTs handle external API calls, enabling unauthorized probes into OpenAI’s Azure cloud infrastructure.
By manipulating URL redirects and authentication headers, Jenkins extracted a valid Azure management token, granting direct access to cloud APIs.
OpenAI quickly patched the issue after it was reported through their bug bounty program, classifying it as high severity.
This case underscores the growing need for robust input validation in AI platforms, especially as they integrate more external interactions.
Unpacking SSRF: A Gateway To Internal Chaos
Server-side request forgery (SSRF) remains a persistent threat in web applications, tricking servers into making unintended network requests on an attacker’s behalf.
Unlike client-side attacks, SSRF leverages the server’s privileged position to reach resources inaccessible from the outside, such as internal databases or cloud metadata endpoints.
According to the OWASP Top 10, SSRF has become increasingly relevant with the shift to cloud-native architectures, where misconfigurations amplify its risks.
In essence, SSRF comes in two flavors: full-read, where attackers snag the response data directly, and blind, where they infer information through timing or side effects.
The cloud twist makes it particularly devastating. Major providers like AWS, Azure, and Google Cloud expose instance metadata services vital for VM configuration at private IP addresses such as 169.254.169.254.
These hold juicy details: instance IDs, network info, and temporary IAM credentials.
A simple SSRF can pivot into a complete environment compromise, as seen in past pentests where attackers commandeered hundreds of EC2 instances via vulnerable invoice tools.
Jenkins’ “hacker sixth sense” kicked in during custom GPT development. These user-created bots extend ChatGPT with tailored instructions, uploaded files, and “Actions” OpenAPI schemas defining external API integrations.
For instance, a weather bot might query a third-party endpoint for forecasts. But without strict URL sanitization, this opens the door to SSRF.
Jenkins aimed to fetch data from his own API but spotted the risk: the system blindly followed user-supplied URLs.
Initial tests failed because Azure’s Instance Metadata Service (IMDS) demands HTTP, while ChatGPT enforced HTTPS.
Enter the classic bypass: a 302 redirect from an attacker-controlled HTTPS server (tools like ssrf.cvssadvisor.com shine here) to the internal HTTP endpoint.
Success the response flowed back, but Azure blocked it sans the “Metadata: true” header, a defense against casual probes.
Bypassing Defenses: From Redirects To Token Theft
Undeterred, Jenkins probed authentication options in the Actions setup. Custom API keys were allowed, so he named one “Metadata” with a value of “true,” slipping the header past restrictions on direct custom headers.
The GPT dutifully returned a live token, verifiable for cloud operations.
While not catastrophic OpenAI’s setup limited privileges this exposed the principle: AI agents phoning “home” to unchecked URLs could leak secrets or enable pivots.
Jenkins reported it promptly via Bugcrowd; OpenAI fixed it swiftly and rewarded the finder.
This exploit reveals AI’s double-edged sword: empowering users while expanding attack surfaces.
Developers must enforce URL allowlisting, block redirects, and harden metadata access. For security pros, it’s a reminder to audit AI integrations like a hawk.
As custom GPTs proliferate, expect more such “spidey-sense” discoveries keeping the cat-and-mouse game alive in cybersecurity.
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