Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS)
CVE-2018-6882 is a medium-severity improper neutralization of input during web page generation 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 8.7.0 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 April 19, 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 8.7.0 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on wiki.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 | before 8.7.0; 8.7.0; 8.8.0; 8.8.1; 8.8.2; 8.8.3; 8.8.4; 8.8.5; and 1 more ranges | 8.7.0 |
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
Cross-site scripting (XSS) vulnerability in the ZmMailMsgView.getAttachmentLinkHtml function in Zimbra Collaboration Suite (ZCS) before 8.7 Patch 1 and 8.8.x before 8.8.7 might allow remote attackers to inject arbitrary web script or HTML via a Content-Location header in an email attachment.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Input During Web Page Generation
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
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. Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
- Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Input During Web Page Generation vulnerabilities (CWE-79)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- seclists.org/fulldisclosure/2018/Mar/52Mailing List, Third Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-6882US Government Resource
Technical write-ups (may include proof of concept)
- securify.nl/advisory/SFY20180101/cross-site-scripting-vulnerability-in-zimbra-collaboration-suite-due-to-the-…Exploit, Third Party Advisory
Other references
- wiki.zimbra.com/wiki/Zimbra_Releases/8.8.7Permissions Required
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 Neutralization of Input During Web Page Generation vulnerabilities
- 6.1 Medium severity
- 5.4 Medium severity
- 6.1 Medium severity
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