VulnerabilityPublished 17 Mar 2026

CVE-2026-27978: vercel next.js · Cross-Site Request Forgery (CSRF)

Affects vercel next.jsSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 16.1.7 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 16.1.7

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
Public exploit code: GitHub proofs of concept
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade vercel next.js to 16.1.7.

Affected software

Product	Affected	Fixed in
vercelnext.js	Affected >=16.0.1 <16.1.7	Fixed in 16.1.7

AI-suggested

Upgrade all Next.js applications to version 16.1.7 or later, which includes the fix treating 'null' as an explicit origin and enforcing strict origin checks.
For environments where immediate upgrading is not possible, implement CSRF tokens on all sensitive Server Actions to ensure requests are validated beyond origin headers.
Configure authentication cookies with the SameSite=Strict attribute to prevent them from being sent with cross-origin requests, reducing CSRF risk.
Review and restrict the experimental.serverActions.allowedOrigins configuration to disallow 'null' unless absolutely necessary, and if allowed, ensure additional protections such as token validation are in place.
Conduct thorough security testing of Server Actions, especially those that change state or perform sensitive operations, to verify that CSRF protections are effective.
Educate developers about the risks of opaque origins and the importance of strict origin validation in web applications.
Monitor application logs for unusual Server Action requests originating from unexpected contexts or origins.
Employ Content Security Policy (CSP) headers to restrict iframe embedding and sandboxing where possible, reducing attack surface for opaque origin exploitation.

Description

CVE-2026-27978 is a Cross-Site Request Forgery (CSRF) vulnerability in Next.js versions 16.0.1 up to but not including 16.1.7. The issue arises because the framework treated 'origin: null' as a missing origin during Server Action CSRF validation, allowing requests from opaque contexts like sandboxed iframes to bypass origin checks. This flaw enables attackers to trick users into submitting unauthorized Server Actions that can change state with the victim's credentials. The vulnerability is fixed in version 16.1.

Impact

This vulnerability allows attackers to perform CSRF attacks against applications using vulnerable Next.js versions, potentially causing unauthorized state changes such as modifying user data, performing transactions, or altering application settings under the victim's session. Since the attack exploits the browser's trust in the user's credentials and session cookies, it can lead to compromised user accounts and unauthorized operations without the victim's explicit consent. The impact is particularly significant for applications handling sensitive data or critical operations, as attackers can manipulate server-side actions that rely on Server Actions. While the vulnerability does not directly expose confidential data or cause denial of service, the integrity of application state and user trust can be severely undermined. Organizations relying on Next.js for web applications face risks of reputational damage, regulatory non-compliance, and potential financial loss if exploited. The medium CVSS score reflects the moderate severity due to the requirement of user interaction and the limited scope of impact to integrity rather than confidentiality or availability.

CWE-352Cross-Site Request Forgery (opens in a new tab)
Compound weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #3OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
Ensure that the application is free of cross-site scripting issues (CWE-79), because most CSRF defenses can be bypassed using attacker-controlled script.
Architecture and Design
Generate a unique nonce for each form, place the nonce into the form, and verify the nonce upon receipt of the form. Be sure that the nonce is not predictable (CWE-330).
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.3 (opens in a new tab)
V4.2.2 (opens in a new tab)
V13.3.2 (opens in a new tab)
Attack patterns
JSON Hijacking (aka JavaScript Hijacking) (opens in a new tab)
Cross-Domain Search Timing (opens in a new tab)
Cross Site Identification (opens in a new tab)
Cross Site Request Forgery (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Mar 2026, 01:03 UTC

Public exploits and detectionGitHub proofs of concept

WeaknessesCWE-352

Technical details

References

Community reviews

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