VulnerabilityPublished 20 Mar 2026Updated 23 Mar 2026

CVE-2026-33372: Zimbra Collaboration · Cross-Site Request Forgery (CSRF)

Source CVE Database V5

Not known to be exploited · CVSS 5.4 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.4Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
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 on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
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), the Metasploit, Exploit-DB and nuclei-templates index as of 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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

AI-suggested

To mitigate CVE-2026-33372, organizations should first verify if they are running affected versions of Zimbra Collaboration Suite (10.0 or 10.1) and prioritize upgrading to a patched version once available. In the absence of an official patch, administrators should implement the following practical measures: 1) Enforce strict Content Security Policy (CSP) headers to restrict the domains from which scripts can be loaded, reducing the risk of malicious script execution. 2) Implement additional server-side validation to ensure CSRF tokens are only accepted via the expected HTTP headers, rejecting tokens supplied in the request body. 3) Educate users about the risks of phishing and social engineering attacks that could trick them into submitting malicious requests. 4) Employ web application firewalls (WAFs) with custom rules to detect and block suspicious requests that include CSRF tokens in unexpected locations. 5) Monitor logs for unusual or unauthorized actions within Zimbra Webmail that could indicate exploitation attempts. 6) Consider deploying multi-factor authentication (MFA) to reduce the impact of session hijacking or misuse. These steps, combined with timely patching, will reduce the risk of exploitation and limit potential damage.

Description

An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A cross-site request forgery (CSRF) vulnerability exists in Zimbra Webmail due to improper validation of CSRF tokens. The application accepts CSRF tokens supplied within the request body instead of requiring them through the expected request header. An attacker can exploit this issue by tricking an authenticated user into submitting a crafted request. This may allow unauthorized actions to be performed on behalf of the victim.

Impact

The primary impact of CVE-2026-33372 is the potential for unauthorized actions to be performed within the Zimbra Webmail environment on behalf of authenticated users. This can lead to limited confidentiality breaches, such as unauthorized access or disclosure of email metadata or content if the attacker can manipulate user actions to reveal such information. Integrity may be compromised if the attacker can cause changes to user settings, send emails, or modify mailbox contents without user consent. Availability is not affected by this vulnerability. Organizations relying on Zimbra Collaboration Suite for email and collaboration services may face risks of account misuse, unauthorized data manipulation, and potential lateral movement if attackers leverage this vulnerability as part of a broader attack chain. The risk is heightened in environments where users frequently access Zimbra Webmail via browsers and may be susceptible to social engineering or phishing attacks that deliver the crafted malicious requests. Although no known exploits are reported in the wild, the vulnerability's ease of exploitation (low complexity and no privileges required) means attackers could develop exploits if motivated. This could impact organizations globally, especially those with large deployments of Zimbra Collaboration Suite versions 10.0 and 10.1.

CWE-352Cross-Site Request Forgery (CSRF) (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

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 27 Mar 2026, 19:19 UTC

WeaknessesCWE-352

Technical details

References

Community reviews

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