CVE-2025-55173Network attack vector

Arbitrary file downloads via trusted upstream content type

Published Aug 29, 2025 · Updated Sep 2, 2025

Content injection in Vercel Next.js before 14.2.31 and 15.0.0 through 15.4.4 allows remote attackers to trigger arbitrary file downloads. The Image Optimization handler trusts an upstream Content-Type header when magic-number detection fails, allowing non-image bytes and an attacker-defined filename to be returned as a download. Exploitation requires images.domains or a permissive images.remotePatterns entry, control of an allowed image server, and user interaction with a crafted URL; the resulting download enables phishing or malicious file delivery.

CVSS severity4.3
Medium
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Content injection in Vercel Next.js before 14.2.31 and 15.0.0 through 15.4.4 allows remote attackers to trigger arbitrary file downloads. The Image Optimization handler trusts an upstream Content-Type header when magic-number detection fails, allowing non-image bytes and an attacker-defined filename to be returned as a download. Exploitation requires images.domains or a permissive images.remotePatterns entry, control of an allowed image server, and user interaction with a crafted URL; the resulting download enables phishing or malicious file delivery.

The record

CVE
CVE-2025-55173
Published
Aug 29, 2025
Updated
Sep 2, 2025
Vendor
Vercel
Product
Next.js
Classifications
CWE-20, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 29, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 14.2.31
  2. Affected versionversion=>= 15.0.0, < 15.4.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vercel · Next.jsversion=< 14.2.31; version=>= 15.0.0, < 15.4.5

Published CVSS scores

4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1204.001Malicious Link

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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