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Low severityNVD Advisory· Published Nov 7, 2025· Updated Dec 1, 2025

CVE-2025-48985

CVE-2025-48985

Description

A vulnerability in Vercel’s AI SDK has been fixed in versions 5.0.52, 5.1.0-beta.9, and 6.0.0-beta. This issue may have allowed users to bypass filetype whitelists when uploading files. All users are encouraged to upgrade.

More details: https://vercel.com/changelog/cve-2025-48985-input-validation-bypass-on-ai-sdk

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

A vulnerability in Vercel's AI SDK allowed bypassing filetype whitelists during file upload, patched in versions 5.0.52, 5.1.0-beta.9, and 6.0.0-beta.

Vulnerability

Overview

CVE-2025-48985 is an input validation bypass vulnerability in Vercel's AI SDK, a TypeScript toolkit for building AI-powered applications. The flaw resides in the file upload functionality, where the SDK's filetype whitelist could be circumvented, allowing users to upload files with disallowed extensions or MIME types [1]. The root cause involves improper validation of file types during the upload process, specifically when handling intermediate file downloads [4].

Exploitation

An attacker could exploit this vulnerability by crafting a file upload request that bypasses the whitelist checks. The attack requires no special privileges beyond the ability to upload files to an application using the vulnerable SDK. By manipulating the file type metadata or leveraging the SDK's download logic for unsupported file types, an attacker could upload arbitrary files that should have been rejected [3][4].

Impact

Successful exploitation could lead to arbitrary file upload, potentially enabling further attacks such as server-side code execution, data exfiltration, or cross-site scripting if uploaded files are served to other users. The severity depends on the application's handling of uploaded files, but the bypass undermines a core security control.

Mitigation

Vercel has released patched versions: 5.0.52, 5.1.0-beta.9, and 6.0.0-beta. All users are strongly encouraged to upgrade immediately [1]. No workarounds have been provided, and the vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities catalog.

References
  1. NVD - CVE-2025-48985
  2. Problem in download logic
  3. Backport: fix(ai): download files when intermediate file cannot be do… · vercel/ai@930399b

AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
ainpm
< 5.0.525.0.52
ainpm
>= 5.1.0-beta.0, < 5.1.0-beta.95.1.0-beta.9

Affected products

2
  • Vercel/AI SDKllm-create
    Range: <5.0.52, <5.1.0-beta.9, <6.0.0-beta
  • Vercel/AI SDKv5
    Range: 5.0.51

Patches

1
930399bb9839

Backport: fix(ai): download files when intermediate file cannot be downloaded (#8883)

https://github.com/vercel/aivercel-ai-sdk[bot]Sep 24, 2025via ghsa
commit
3 files changed · +108 −11
  • .changeset/tall-terms-smash.md+5 −0 added
    @@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+fix(ai): download files when intermediate file cannot be downloaded
  • packages/ai/src/prompt/convert-to-language-model-prompt.test.ts+95 −0 modified
    @@ -673,6 +673,101 @@ describe('convertToLanguageModelPrompt', () => {
         ]);
       });
     });
+
+    it('should download files when intermediate file cannot be downloaded', async () => {
+      const imageUrlA = `http://example.com/my-image-A.png`; // supported
+      const fileUrl = `http://127.0.0.1:3000/file`; // unsupported
+      const imageUrlB = `http://example.com/my-image-B.png`; // supported
+
+      const mockDownload = vi.fn().mockResolvedValue([
+        {
+          url: new URL(imageUrlA),
+          data: new Uint8Array([137, 80, 78, 71, 13, 10, 26, 10, 0]), // empty png and 0
+          mediaType: 'image/png',
+        },
+        null,
+        {
+          url: new URL(imageUrlB),
+          data: new Uint8Array([137, 80, 78, 71, 13, 10, 26, 10, 1]), // empty png and 1
+          mediaType: 'image/png',
+        },
+      ]);
+
+      const result = await convertToLanguageModelPrompt({
+        prompt: {
+          messages: [
+            {
+              role: 'user',
+              content: [
+                { type: 'image', image: imageUrlA, mediaType: 'image/png' },
+                {
+                  type: 'file',
+                  data: new URL(fileUrl),
+                  mediaType: 'application/octet-stream',
+                },
+                { type: 'image', image: imageUrlB, mediaType: 'image/png' },
+              ],
+            },
+          ],
+        },
+        supportedUrls: {
+          '*': [/^https:\/\/.*$/],
+        },
+        download: mockDownload,
+      });
+
+      expect(result).toMatchInlineSnapshot(`
+        [
+          {
+            "content": [
+              {
+                "data": Uint8Array [
+                  137,
+                  80,
+                  78,
+                  71,
+                  13,
+                  10,
+                  26,
+                  10,
+                  0,
+                ],
+                "filename": undefined,
+                "mediaType": "image/png",
+                "providerOptions": undefined,
+                "type": "file",
+              },
+              {
+                "data": "http://127.0.0.1:3000/file",
+                "filename": undefined,
+                "mediaType": "application/octet-stream",
+                "providerOptions": undefined,
+                "type": "file",
+              },
+              {
+                "data": Uint8Array [
+                  137,
+                  80,
+                  78,
+                  71,
+                  13,
+                  10,
+                  26,
+                  10,
+                  1,
+                ],
+                "filename": undefined,
+                "mediaType": "image/png",
+                "providerOptions": undefined,
+                "type": "file",
+              },
+            ],
+            "providerOptions": undefined,
+            "role": "user",
+          },
+        ]
+      `);
+    });
   });
 
   describe('custom download function', () => {
  • packages/ai/src/prompt/convert-to-language-model-prompt.ts+8 −11 modified
    @@ -245,18 +245,15 @@ async function downloadAssets(
 
   return Object.fromEntries(
     downloadedFiles
-      .filter(
-        (
-          downloadedFile,
-        ): downloadedFile is {
-          mediaType: string | undefined;
-          data: Uint8Array;
-        } => downloadedFile?.data != null,
+      .map((file, index) =>
+        file == null
+          ? null
+          : [
+              plannedDownloads[index].url.toString(),
+              { data: file.data, mediaType: file.mediaType },
+            ],
       )
-      .map(({ data, mediaType }, index) => [
-        plannedDownloads[index].url.toString(),
-        { data, mediaType },
-      ]),
+      .filter(file => file != null),
   );
 }

Vulnerability mechanics

Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

5

News mentions

0

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