fix(security): add URL validation to prevent SSRF in download functions#13085
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fix(security): add URL validation to prevent SSRF in download functions#13085
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Add validateDownloadUrl utility that blocks private/internal addresses, non-HTTP protocols, and localhost before fetching user-provided URLs in downloadBlob and download functions. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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…vent SSRF bypass (#13111) ## Background The existing `validateDownloadUrl` (added in #13085) only validates the initial URL before `fetch()`. Since `fetch()` follows HTTP redirects by default, an attacker can bypass SSRF protections by providing a safe-looking public URL that 302-redirects to internal endpoints (e.g., `http://169.254.169.254/latest/meta-data/`), enabling in-band response body exfiltration through the AI model's response. ## Summary Added `response.redirected` check with `validateDownloadUrl(response.url)` in both `downloadBlob` (`@ai-sdk/provider-utils`) and `download` (`ai`) functions to validate the final URL after following redirects, before reading the response body. ## Manual Verification - `pnpm vitest run packages/provider-utils/src/download-blob.test.ts` — 16 tests pass - `pnpm vitest run packages/provider-utils/src/validate-download-url.test.ts` — 29 tests pass - `pnpm vitest run packages/ai/src/util/download/download.test.ts -t "SSRF"` — 5 tests pass
vercel-ai-sdk bot
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Mar 5, 2026
…vent SSRF bypass (#13111) ## Background The existing `validateDownloadUrl` (added in #13085) only validates the initial URL before `fetch()`. Since `fetch()` follows HTTP redirects by default, an attacker can bypass SSRF protections by providing a safe-looking public URL that 302-redirects to internal endpoints (e.g., `http://169.254.169.254/latest/meta-data/`), enabling in-band response body exfiltration through the AI model's response. ## Summary Added `response.redirected` check with `validateDownloadUrl(response.url)` in both `downloadBlob` (`@ai-sdk/provider-utils`) and `download` (`ai`) functions to validate the final URL after following redirects, before reading the response body. ## Manual Verification - `pnpm vitest run packages/provider-utils/src/download-blob.test.ts` — 16 tests pass - `pnpm vitest run packages/provider-utils/src/validate-download-url.test.ts` — 29 tests pass - `pnpm vitest run packages/ai/src/util/download/download.test.ts -t "SSRF"` — 5 tests pass
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Background
The
downloadBlobfunction (@ai-sdk/provider-utils) anddownloadfunction (ai) fetch user-provided URLs without any validation. When users pass image URLs togenerateImage(), strings starting with "http" flow directly tofetch()viadownloadBlob(file.url)in OpenAI, OpenAI-compatible, and DeepInfra image models. This enables blind SSRF — attackers can make the server request internal resources (localhost, cloud metadata endpoints like169.254.169.254, private IPs).Summary
Added a shared
validateDownloadUrlutility in@ai-sdk/provider-utilsthat bothdownloadBlobanddownloadcall beforefetch. It throwsDownloadErrorif the URL is unsafe:http:andhttps:allowedlocalhost,*.local,*.localhost, empty hostname127.0.0.0/8,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,169.254.0.0/16,0.0.0.0/8::1,fc00::/7,fe80::/10,::, and IPv4-mapped addresses (::ffff:x.x.x.x)No DNS resolution checks (not available in edge runtimes). Reuses
DownloadErrorfor rejected URLs.Manual Verification
pnpm vitest run src/validate-download-url.test.tsinpackages/provider-utils— 29 tests passpnpm vitest run src/download-blob.test.tsinpackages/provider-utils— 13 tests passpnpm vitest run src/util/download/download.test.tsinpackages/ai— 7 tests passChecklist
pnpm changesetin the project root)Future Work