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CVE-2022-21721

DOS Vulnerability in next.js

5.9 MediumFix available

Next.js is a React framework. Starting with version 12.0.0 and prior to version 12.0.9, vulnerable code could allow a bad actor to trigger a denial of service attack for anyone using i18n functionality. In order to be affected by this CVE, one must use next start or a custom server and the built-in i18n support. Deployments on Vercel, along with similar environments where invalid requests are filtered before reaching Next.js, are not affected. A patch has been released, [email protected], that mitigates this issue. As a workaround, one may ensure /${locale}/_next/ is blocked from reaching the Next.js instance until it becomes feasible to upgrade.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

2.15%Up 1.2 points since Feb 8, 2022
90%50%10%1%

What each source reports

CVE List Score used 5.9

DOS Vulnerability in next.js

Next.js is a React framework. Starting with version 12.0.0 and prior to version 12.0.9, vulnerable code could allow a bad actor to trigger a denial of service attack for anyone using i18n functionality. In order to be affected by this CVE, one must use next start or a custom server and the built-in i18n support. Deployments on Vercel, along with similar environments where invalid requests are filtered before reaching Next.js, are not affected. A patch has been released, [email protected], that mitigates this issue. As a workaround, one may ensure /${locale}/_next/ is blocked from reaching the Next.js instance until it becomes feasible to upgrade.

Record
CVE-2022-21721
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
EUVDEUVD-2022-0727 5.9

Next.js is a React framework. Starting with version 12.0.0 and prior to version 12.0.9, vulnerable code could allow a bad actor to trigger a denial of service attack for anyone using i18n functionality. In order to be affected by this CVE, one must use next start or a custom server and the built-in i18n support. Deployments on Vercel, along with similar environments where invalid requests are filtered before reaching Next.js, are not affected. A patch has been released, [email protected], that mitigates this issue. As a workaround, one may ensure /${locale}/_next/ is blocked from reaching the Next.js instance until it becomes feasible to upgrade.

Record
EUVD-2022-0727
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-wr66-vrwm-5g5x 5.9

Denial of Service Vulnerability in next.js

Impact

Vulnerable code could allow a bad actor to trigger a denial of service attack for anyone running a Next.js app at version >= 12.0.0, and using i18n functionality.

  • Affected: All of the following must be true to be affected by this CVE
    • Next.js versions above v12.0.0
    • Using next start or a custom server
    • Using the built-in i18n support
  • Not affected:
    • Deployments on Vercel (vercel.com) are not affected along with similar environments where invalid requests are filtered before reaching Next.js.

Patches

A patch has been released, [email protected], that mitigates this issue. We recommend all affected users upgrade as soon as possible.

Workarounds

We recommend upgrading whether you can reproduce or not although you can ensure /${locale}/_next/ is blocked from reaching the Next.js instance until you upgrade.

For more information

If you have any questions or comments about this advisory:

Record
GHSA-wr66-vrwm-5g5x
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-20, CWE-400
Updated
2026-11-02
NVD 5.9

Next.js is a React framework. Starting with version 12.0.0 and prior to version 12.0.9, vulnerable code could allow a bad actor to trigger a denial of service attack for anyone using i18n functionality. In order to be affected by this CVE, one must use next start or a custom server and the built-in i18n support. Deployments on Vercel, along with similar environments where invalid requests are filtered before reaching Next.js, are not affected. A patch has been released, [email protected], that mitigates this issue. As a workaround, one may ensure /${locale}/_next/ is blocked from reaching the Next.js instance until it becomes feasible to upgrade.

Record
CVE-2022-21721
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:N/A:P
Updated
2026-11-02
OSV 5.9

DOS Vulnerability in next.js

Next.js is a React framework. Starting with version 12.0.0 and prior to version 12.0.9, vulnerable code could allow a bad actor to trigger a denial of service attack for anyone using i18n functionality. In order to be affected by this CVE, one must use next start or a custom server and the built-in i18n support. Deployments on Vercel, along with similar environments where invalid requests are filtered before reaching Next.js, are not affected. A patch has been released, [email protected], that mitigates this issue. As a workaround, one may ensure /${locale}/_next/ is blocked from reaching the Next.js instance until it becomes feasible to upgrade.

Record
CVE-2022-21721
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVGHSA-wr66-vrwm-5g5x 5.9

Denial of Service Vulnerability in next.js

Impact

Vulnerable code could allow a bad actor to trigger a denial of service attack for anyone running a Next.js app at version >= 12.0.0, and using i18n functionality.

  • Affected: All of the following must be true to be affected by this CVE
    • Next.js versions above v12.0.0
    • Using next start or a custom server
    • Using the built-in i18n support
  • Not affected:
    • Deployments on Vercel (vercel.com) are not affected along with similar environments where invalid requests are filtered before reaching Next.js.

Patches

A patch has been released, [email protected], that mitigates this issue. We recommend all affected users upgrade as soon as possible.

Workarounds

We recommend upgrading whether you can reproduce or not although you can ensure /${locale}/_next/ is blocked from reaching the Next.js instance until you upgrade.

For more information

If you have any questions or comments about this advisory:

Record
GHSA-wr66-vrwm-5g5x
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-20, CWE-400
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
next
npm
 12.0.0 up to 12.0.9
12.0.9

History

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

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

In short

CVE-2022-21721 is a medium vulnerability (CVSS 5.9) in Vercel Next.js, published January 28, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.15%, the 82nd percentile. Fixed in next 12.0.9.

References

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