Synacor Zimbra Collaborate Suite (ZCS) Cross-Site Scripting
CVE-2022-24682 is a medium-severity improper encoding or escaping of output vulnerability in Zimbra Collaboration Suite from Synacor, with a CVSS 3.1 base score of 6.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 8.8.15 as the first without the flaw, so updating Zimbra Collaboration Suite to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on February 25, 2022, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Zimbra Collaboration Suite to 8.8.15 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on blog.zimbra.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Synacor | Zimbra Collaboration Suite | 8.8.0 up to, but not including, 8.8.15; 8.8.15 | 8.8.15 |
Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 6.1 | Medium | NVD |
| CVSS 3.1 | 6.1 | Medium | CISA (ADP) |
| CVSS 2.0 | 4.3 | Medium | NVD |
Official description
An issue was discovered in the Calendar feature in Zimbra Collaboration Suite 8.8.x before 8.8.15 patch 30 (update 1), as exploited in the wild starting in December 2021. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Encoding or Escaping of Output
The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
How developers prevent this class of flaw
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using the ESAPI Encoding control or a similar tool, library, or framework. These will help the programmer encode outputs in a manner less prone to error. Alternately, use built-in functions, but consider using wrappers in case those functions are discovered to have a vulnerability.
- If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated. For example, stored procedures can enforce database query structure and reduce the likelihood of SQL injection.
- Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.
More Improper Encoding or Escaping of Output vulnerabilities (CWE-116)
Timeline
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: partial).
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2022-24682US Government Resource
Technical write-ups (may include proof of concept)
- volexity.com/blog/2022/02/03/operation-emailthief-active-exploitation-of-zero-day-xss-vulnerability-in-zimbra/Exploit, Third Party Advisory
Other vulnerabilities in Zimbra Collaboration Suite
- 8.9 High severity
- 8.8 High severity
- 6.1 Medium severity
- 8.8 High severity
- 6.1 Medium severity
- 8.8 High severity
Recent Improper Encoding or Escaping of Output vulnerabilities
- 9.8 Critical severity
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