CVE-2026-64799: Content-Controlled Image SSRF Vulnerability

CVE-2026-64799 Overview

CVE-2026-64799 is a Server-Side Request Forgery (SSRF) vulnerability [CWE-918] affecting an image fetching feature that accepts content-controlled URLs. The application requests remote resources without validating the destination host, follows unsafe redirects, and stores response bodies without confirming they are valid image data. Attackers can coerce the server into contacting private or reserved network ranges, exfiltrate internal service responses, and write attacker-controlled files into a web-accessible directory. The vulnerability was published to the National Vulnerability Database (NVD) on 2026-07-23 and references materials published by Regular Labs.

Critical Impact
Remote actors can trigger internal network requests, retrieve responses from private services, and drop arbitrary files into web-accessible folders — enabling SSRF, internal data disclosure, and potential remote code execution through uploaded content.

Affected Products

Product details were not published in the NVD entry at time of writing
See the Regular Labs Security Resource for vendor-specific product mapping
Any deployment exposing the affected image fetch functionality to untrusted input should be treated as vulnerable

Discovery Timeline

2026-07-23 - CVE-2026-64799 published to NVD
2026-07-23 - Last updated in NVD database

Technical Details for CVE-2026-64799

Vulnerability Analysis

The application fetches images from URLs supplied through content that can be influenced by an attacker. Because the fetcher does not enforce an allowlist of destinations, it can be pointed at internal endpoints such as cloud metadata services, loopback interfaces, or reserved IP ranges. The server processes and stores the response as if it were an image, giving the attacker two distinct primitives from a single request.

The first primitive is SSRF. The vulnerable code performs an outbound HTTP request from the server's network position, allowing attackers to probe internal infrastructure that is not directly reachable from the internet. The second primitive is unrestricted file write. Response bodies are persisted to disk under an image extension without verifying the content type or magic bytes.

Root Cause

The root cause is missing validation on three layers of the fetch pipeline. The URL scheme and host are not filtered against a deny list of private ranges (RFC1918, loopback, link-local, cloud metadata). HTTP redirects are followed without re-validating the redirect target, letting attackers bypass any host check by redirecting from a public host to an internal one. Response content is written to storage without confirming that the bytes represent an image format.

Attack Vector

An attacker injects a crafted URL into any content field that feeds the image fetcher. The server issues an outbound request to the attacker-supplied host, follows a redirect that points to http://169.254.169.254/ or http://127.0.0.1/, and stores the returned payload in a web-accessible directory. Because the destination path is inside the web root, the attacker can then request the stored file directly and read the exfiltrated response or execute the file if the server processes it as script.

Detection Methods for CVE-2026-64799

Indicators of Compromise

Outbound HTTP requests from application servers to RFC1918, loopback, or link-local addresses originating from image-fetch worker processes
New files in web-accessible upload directories with image extensions but non-image magic bytes (e.g., HTML, JSON, or script content)
HTTP redirects in application logs where the initial host is public but the final host resolves to a private range

Detection Strategies

Inspect application logs for image fetch operations targeting non-image content types in HTTP responses
Correlate egress traffic from application tiers with expected image CDN destinations and alert on deviations
Baseline the entropy and MIME signatures of files written to upload directories and flag anomalies

Monitoring Recommendations

Enable egress filtering at the network layer and log all denied connections from application subnets
Monitor cloud metadata endpoint access (169.254.169.254) from any workload that does not require it
Track file writes into /uploads, /images, or equivalent web-accessible paths and alert on non-image content

How to Mitigate CVE-2026-64799

Immediate Actions Required

Apply the vendor patch referenced by the Regular Labs Security Resource once the fix is available for your deployment
Restrict outbound network access from application servers to only the domains required for legitimate image sourcing
Audit web-accessible upload directories for recently created files with mismatched content types and quarantine suspicious artifacts

Patch Information

Refer to the Regular Labs Security Resource for the authoritative patch and version guidance. At the time of the NVD entry (2026-07-23), no specific fixed version strings were enumerated in the CVE record. Administrators should confirm patch level with the vendor and validate that URL validation, redirect handling, and content-type verification are enforced in the updated release.

Workarounds

Disable or gate the image-by-URL feature behind authenticated administrator access until a patch is deployed
Enforce an allowlist of external image hosts and reject requests to any private, reserved, or metadata IP range
Reject HTTP redirects during image fetches, or re-validate the redirect target against the allowlist before following
Verify response Content-Type and magic bytes match a permitted image format before writing to disk, and store fetched files outside the web root

bash

# Configuration example: egress deny list for image fetch worker (iptables)
iptables -A OUTPUT -m owner --uid-owner www-data -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 192.168.0.0/16 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 127.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner www-data -d 169.254.0.0/16 -j REJECT