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CVE-2021-39178

XSS in Image Optimization API for Next.js versions between 10.0.0 and 11.1.0

7.5 HighFix available

Next.js is a React framework. Versions of Next.js between 10.0.0 and 11.0.0 contain a cross-site scripting vulnerability. In order for an instance to be affected by the vulnerability, the next.config.js file must have images.domains array assigned and the image host assigned in images.domains must allow user-provided SVG. If the next.config.js file has images.loader assigned to something other than default or the instance is deployed on Vercel, the instance is not affected by the vulnerability. The vulnerability is patched in Next.js version 11.1.1.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

1.14%Up 0.5 points since Aug 31, 2021
90%50%10%1%

What each source reports

CVE List Score used 7.5

XSS in Image Optimization API for Next.js versions between 10.0.0 and 11.1.0

Next.js is a React framework. Versions of Next.js between 10.0.0 and 11.0.0 contain a cross-site scripting vulnerability. In order for an instance to be affected by the vulnerability, the next.config.js file must have images.domains array assigned and the image host assigned in images.domains must allow user-provided SVG. If the next.config.js file has images.loader assigned to something other than default or the instance is deployed on Vercel, the instance is not affected by the vulnerability. The vulnerability is patched in Next.js version 11.1.1.

Record
CVE-2021-39178
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-79
Updated
2026-11-02
EUVDEUVD-2021-2024 7.5

Next.js is a React framework. Versions of Next.js between 10.0.0 and 11.0.0 contain a cross-site scripting vulnerability. In order for an instance to be affected by the vulnerability, the next.config.js file must have images.domains array assigned and the image host assigned in images.domains must allow user-provided SVG. If the next.config.js file has images.loader assigned to something other than default or the instance is deployed on Vercel, the instance is not affected by the vulnerability. The vulnerability is patched in Next.js version 11.1.1.

Record
EUVD-2021-2024
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-03
GitHub AdvisoriesGHSA-9gr3-7897-pp7m 7.5

XSS in Image Optimization API for Next.js

Impact

  • Affected: All of the following must be true to be affected
    • Next.js between version 10.0.0 and 11.1.0
    • The next.config.js file has images.domains array assigned
    • The image host assigned in images.domains allows user-provided SVG
  • Not affected: The next.config.js file has images.loader assigned to something other than default
  • Not affected: Deployments on Vercel are not affected

Patches

Next.js v11.1.1

Record
GHSA-9gr3-7897-pp7m
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-79
Updated
2026-11-02
NVD 7.5

Next.js is a React framework. Versions of Next.js between 10.0.0 and 11.0.0 contain a cross-site scripting vulnerability. In order for an instance to be affected by the vulnerability, the next.config.js file must have images.domains array assigned and the image host assigned in images.domains must allow user-provided SVG. If the next.config.js file has images.loader assigned to something other than default or the instance is deployed on Vercel, the instance is not affected by the vulnerability. The vulnerability is patched in Next.js version 11.1.1.

Record
CVE-2021-39178
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:P/A:N
Weakness
CWE-79
Updated
2026-11-02
OSV 6.1

Next.js is a React framework. Versions of Next.js between 10.0.0 and 11.0.0 contain a cross-site scripting vulnerability. In order for an instance to be affected by the vulnerability, the next.config.js file must have images.domains array assigned and the image host assigned in images.domains must allow user-provided SVG. If the next.config.js file has images.loader assigned to something other than default or the instance is deployed on Vercel, the instance is not affected by the vulnerability. The vulnerability is patched in Next.js version 11.1.1.

Record
CVE-2021-39178
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVGHSA-9gr3-7897-pp7m 7.5

XSS in Image Optimization API for Next.js

Impact

  • Affected: All of the following must be true to be affected
    • Next.js between version 10.0.0 and 11.1.0
    • The next.config.js file has images.domains array assigned
    • The image host assigned in images.domains allows user-provided SVG
  • Not affected: The next.config.js file has images.loader assigned to something other than default
  • Not affected: Deployments on Vercel are not affected

Patches

Next.js v11.1.1

Record
GHSA-9gr3-7897-pp7m
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-79
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
next
npm
 10.0.0 up to 11.1.1
11.1.1

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-39178 is a high vulnerability (CVSS 7.5) in Vercel Next.js, published August 30, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.14%, the 66th percentile. Fixed in next 11.1.1.

References

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