CVE-2026-44492: Axios: shouldBypassProxy does not recognize IPv4-mapped IPv6 addresses, allowing NO_PROXY bypass (incomplete fix for CVE-2025-62718)

Synopsis

A proxy-bypass vulnerability exists in Axios, a widely used HTTP client for Node.js and browsers. An attacker who can influence request URLs can craft an IPv4-mapped IPv6 address (for example ::ffff:7f00:1 in place of 127.0.0.1) to route requests through a configured proxy even when the target IP is listed in NO_PROXY, because Axios does not normalize these address forms before checking the bypass list. Successful exploitation allows the attacker to read responses from internal services such as instance metadata endpoints, exposing sensitive configuration data and credentials. HarborGuard tracks this advisory and will make a patched-image rebuild available as soon as fix versions are published upstream.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must be able to send requests over the network to an Axios-backed service or influence its outbound HTTP requests remotely.

• AuthenticationNot required

  No authentication is required; the bypass is triggered purely by the form of the request URL, with no credential needed.

• Victim interactionNot required

  No victim interaction is needed; the malformed IPv4-mapped IPv6 address is processed automatically by the Axios request pipeline.

• Attack complexityDetail

  Attack complexity is low; exploiting the bypass requires only constructing a well-known IPv4-mapped IPv6 address form and no special environmental conditions or race conditions.

Blast Radius

• Reads responses from internal HTTP services (such as cloud instance metadata endpoints at 169.254.169.254) that are intended to be unreachable via proxy, exposing IAM credentials, instance identity tokens, and bootstrap secrets.
• Reads data from loopback services at 127.0.0.1 that the NO_PROXY list was meant to protect, such as local admin APIs or sidecar services.
• The scope impact is changed (S:C in CVSS), meaning the confidentiality breach extends beyond the vulnerable Axios process itself to any downstream system whose secrets are exposed through the metadata or internal service responses.