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Security Advisory: Unbounded Download DoS Prevention

Status: Fixed Severity: High CVE: TBD Affected Versions: All versions before v0.X.X Fixed in: v0.X.X

Summary​

Prior versions of the Go-AI SDK allowed unbounded memory growth when downloading from user-provided URLs (images, videos, audio), enabling Denial of Service (DoS) attacks through memory exhaustion.

Vulnerability Details​

Attack Vector​

The SDK's download functions did not limit file sizes when fetching resources from user-provided URLs. An attacker could provide URLs pointing to extremely large files (e.g., 100GB+), causing:

  • Memory exhaustion
  • Process crashes from Out-of-Memory (OOM) errors
  • Resource depletion on the host system
  • Service unavailability

Example Attack​

// Attacker provides URL to a huge file
model := xai.NewImageModel(xaiProvider, "grok-2-vision-1212")
result, err := ai.GenerateImage(ctx, ai.GenerateImageOptions{
    Model:  model,
    Prompt: "analyze this image",
    Files: []provider.ImageFile{
        {Type: "url", URL: "https://evil.com/100gb-file.jpg"}, // Causes OOM crash
    },
})
// Process crashes from memory exhaustion

Affected Components​

  • Image download functions in providers (XAI, BFL, FAL, Replicate)
  • Video download functions in providers (Google, FAL, Replicate)
  • Any code path that downloads from user-provided URLs

Fix​

Changes​

The fix implements a 2 GiB default size limit for all downloads with the following protections:

  1. Early rejection: Checks Content-Length header before downloading
  2. Streaming with limits: Reads response body incrementally with io.LimitReader
  3. Proper error handling: Throws DownloadError when limit exceeded
  4. Context cancellation: Respects context cancellation for aborting downloads

Default Protection​

All download operations now automatically enforce a 2 GiB limit. The default download function (used internally, and available via ai.CreateURLDownload for your own code) enforces this limit without any extra configuration:

// Automatically protected with 2 GiB limit
download := ai.CreateURLDownload(nil)
data, err := download(ctx, url)

Custom Limits​

Applications can configure custom size limits:

// Create single-URL download function with custom 100 MB limit
customDownload := ai.CreateURLDownloadWithMetadata(&ai.DownloadOptions{
    MaxBytes: 100 * 1024 * 1024, // 100 MB
})

// Use in generation functions
result, err := ai.GenerateVideo(ctx, ai.GenerateVideoOptions{
    Model: model,
    Prompt: videoPrompt,
    DownloadWithMetadata: customDownload,
})

Mitigation​

Immediate Action​

Upgrade to v0.X.X or later immediately. No workaround is available for earlier versions.

Version Check​

go list -m github.com/digitallysavvy/go-ai

If the version is below v0.X.X, upgrade with:

go get github.com/digitallysavvy/go-ai@latest

Impact Assessment​

Who is Affected?​

Any application that:

  • Accepts user-provided image/video/audio URLs
  • Uses the Go-AI SDK for generation with file inputs
  • Runs in production environments with untrusted input

Risk Level​

  • High for public-facing services with user-generated content
  • Medium for internal services with trusted users
  • Low for applications that only use SDK-generated content

Timeline​

  • Discovered: 2026-02-12
  • Fixed: 2026-02-15
  • Released: 2026-02-XX
  • Public Disclosure: 2026-02-XX

Credits​

Security fix implemented based on TypeScript AI SDK commit 4024a3af6.

References​

Contact​

For security concerns, please report to: security@digitallysavvy.com