CVE-2026-85242: Server-Side Request Forgery via Favicon Redirect to Local Network Resources in PlaywrightCapture
PlaywrightCapture contains a server-side request forgery (SSRF) vulnerability in its favicon retrieval functionality. When onlygloballookup is enabled, the application validates the initial favicon URL to prevent requests to localhost, loopback, or other non-public network addresses. However, redirects followed by aiohttp were not subjected to the same validation.
An attacker able to influence the content of a page processed by PlaywrightCapture could specify a publicly reachable favicon URL that responds with an HTTP redirect to a local or otherwise restricted address, such as 127.0.0.1, localhost, or an internal network service. Because aiohttp automatically followed the redirect, the resulting request could bypass the application's local-address restrictions and cause the PlaywrightCapture host to issue HTTP requests to resources that should not be externally reachable.
Depending on the services reachable from the PlaywrightCapture host and how retrieved favicon data is subsequently exposed or processed, this could be used to probe internal HTTP services or potentially obtain information from otherwise inaccessible endpoints.
The patch introduces an aiohttp request middleware that applies the existing local-URL validation to every request in the redirect chain. Requests resolving to restricted/local destinations are rejected before they are issued.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
When only_global_lookup is enabled, ensure the application validates the initial favicon URL to prevent requests to localhost/loopback or other non-public network addresses.
PlaywrightCapture only_global_lookup = enabled - Configuration
Apply the patch that adds an aiohttp request middleware so that the existing local-URL validation is enforced for every request in the favicon redirect chain (not just the initial URL).
PlaywrightCapture aiohttp redirect handling (SSRF mitigation middleware) = apply existing local-URL validation to all redirect-chain requests
Event History
Frequently Asked Questions
Who can trigger this issue?
An attacker must be able to influence the content of a page that PlaywrightCapture processes, including specifying its favicon URL. The issue is relevant when that favicon URL can point to a publicly reachable server controlled by the attacker.
Is the default configuration affected?
The described bypass requires only_global_lookup to be enabled. The provided information does not state whether this setting is enabled by default.
What does an attacker need to make the PlaywrightCapture host request an internal service?
The attacker needs a public favicon URL that passes the initial address validation and returns an HTTP redirect to localhost, a loopback address, or another restricted internal address. aiohttp then automatically follows that redirect without applying the same validation.
What can be done if the patch cannot be applied immediately?
Disable only_global_lookup if doing so is acceptable for the deployment, or prevent PlaywrightCapture from reaching local and internal HTTP services through network-level egress controls. Restrict processing of attacker-influenced pages where possible.