CVE-2026-82957: Hyperledger Firefly SSRF Vulnerability

CVE-2026-82957 Overview

CVE-2026-82957 is a server-side request forgery (SSRF) vulnerability affecting Hyperledger FireFly versions up to 1.4.0. The flaw resides in the ValidateOptions function within internal/events/webhooks/webhooks.go, part of the Webhook Subscription component. Attackers can manipulate the url argument to coerce the FireFly service into issuing arbitrary outbound HTTP requests. Remote exploitation requires no authentication or user interaction. The exploit has been published, and the vendor did not respond to disclosure attempts. This weakness is categorized under CWE-918: Server-Side Request Forgery.

Critical Impact
Unauthenticated remote attackers can abuse FireFly webhook subscriptions to probe internal networks, reach cloud metadata endpoints, and pivot against services otherwise inaccessible from the internet.

Affected Products

Hyperledger FireFly versions up to and including 1.4.0
FireFly Webhook Subscription component (internal/events/webhooks/webhooks.go)
Deployments exposing the FireFly API for subscription management

Discovery Timeline

2026-08-31 - CVE-2026-82957 published to NVD
2026-09-01 - Last updated in NVD database

Technical Details for CVE-2026-82957

Vulnerability Analysis

Hyperledger FireFly is a multiparty system that enables enterprise applications to build on blockchain and Web3 stacks. FireFly supports webhook subscriptions, allowing consumers to register an HTTP endpoint that receives event notifications. The ValidateOptions function in internal/events/webhooks/webhooks.go is responsible for validating subscription options, including the target url supplied by the subscriber.

The function does not sufficiently restrict the destination URL. Attackers can register a subscription whose callback points to internal-only resources such as 127.0.0.1, 169.254.169.254, private RFC 1918 ranges, or internal service names. When FireFly dispatches events, it issues outbound HTTP requests to these destinations and, depending on configuration, returns response data or error content to the requester.

Root Cause

The root cause is missing URL allow-listing and blocklisting in ValidateOptions. The function accepts arbitrary schemes and hostnames without verifying that the target is a legitimate external webhook consumer. It also lacks DNS rebinding protection and does not validate the resolved IP address before dispatching requests.

Attack Vector

An attacker with the ability to create or modify webhook subscriptions submits a subscription containing a crafted url value that targets an internal resource. The FireFly server then performs outbound requests against that target when events fire. This behavior enables port scanning, interaction with unauthenticated internal APIs, and retrieval of cloud instance metadata credentials. Exploitation occurs over the network and does not require authentication in default deployments that expose the subscription API.

No verified proof-of-concept code is included in the referenced advisories. See the VulDB entry for CVE-2026-82957 for additional technical context.

Detection Methods for CVE-2026-82957

Indicators of Compromise

Webhook subscription entries containing URLs pointing to localhost, 127.0.0.0/8, 169.254.169.254, or RFC 1918 private address space.
Outbound HTTP requests from the FireFly service process to internal-only hosts or cloud metadata endpoints.
Unexpected subscription creation events in FireFly audit logs originating from untrusted API clients.

Detection Strategies

Inspect FireFly subscription records and audit configured webhook URLs for internal or loopback destinations.
Correlate FireFly process network telemetry with expected external webhook consumers, flagging anomalies.
Deploy egress inspection rules that alert when the FireFly host attempts to contact metadata services or private ranges.

Monitoring Recommendations

Log and review all POST requests to the FireFly /subscriptions API and record submitting identities and payloads.
Monitor DNS resolutions performed by the FireFly host for suspicious hostnames that resolve to internal IPs.
Alert on repeated 4xx or 5xx outbound responses that indicate scanning behavior against internal endpoints.

How to Mitigate CVE-2026-82957

Immediate Actions Required

Restrict access to the FireFly subscription API to trusted, authenticated clients only using network segmentation and reverse-proxy authentication.
Enumerate existing webhook subscriptions and remove any pointing to internal or loopback addresses.
Place FireFly egress traffic behind a filtering proxy that blocks requests to private ranges and cloud metadata endpoints.

Patch Information

At the time of publication, no vendor patch has been referenced in the advisory sources. The disclosure notes state the vendor did not respond to contact attempts. Monitor the Hyperledger FireFly repository for fixed releases beyond 1.4.0, and consult the VulDB advisory for updates.

Workarounds

Deploy an outbound web proxy in front of FireFly and configure it to deny requests to 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, and 169.254.169.254.
Enforce cloud provider IMDSv2 with hop-limit hardening to prevent metadata credential theft via SSRF.
Apply a network policy that restricts the FireFly workload to only reach known, allow-listed webhook consumer domains.

bash

# Example iptables egress restrictions for the FireFly host
iptables -A OUTPUT -m owner --uid-owner firefly -d 127.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner firefly -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner firefly -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner firefly -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner firefly -d 192.168.0.0/16 -j REJECT