Cyber Resilience

CVE-2023-34192

XSS in Synacor Zimbra Collaboration Suite 8.8.15

CISA KEVActive ExploitationEUVD ExploitedXSS
Published
06 July 2023
Modified
27 October 2025
KEV Added
25 February 2025
Patch / advisory
CVSS Score v3.1 9.0
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
EPSS Score 0.77 99.5th percentile
Risk Priority 85 floored blend · peak EPSS

Summary

CVE-2023-34192 is a critical-severity Cross-site Scripting (CWE-79) vulnerability in Synacor Zimbra Collaboration Suite. Its CVSS base score is 9.0 (Critical).

Operationally, ranked in the top 0.5% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SI-15 (Information Output Filtering) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2023-34192 is a cross-site scripting vulnerability (CWE-79) affecting Zimbra Collaboration Suite (ZCS) version 8.8.15. The flaw resides in the /h/autoSaveDraft function and permits injection of arbitrary scripts that execute in the context of other users.

A remote attacker who already possesses a valid account can supply a crafted payload to the affected endpoint. Successful exploitation yields arbitrary code execution with confidentiality, integrity, and availability impacts rated high under CVSS 3.1; the changed scope metric indicates the attack can affect resources beyond the initial component.

Zimbra publishes security advisories and patches through its Security Center and responsible-disclosure pages; administrators should apply the vendor-supplied updates referenced in those advisories to remediate the issue. The associated EPSS score remains elevated near 0.90, indicating sustained exploitation interest following disclosure.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Cross Site Scripting vulnerability in Zimbra ZCS v.8.8.15 allows a remote authenticated attacker to execute arbitrary code via a crafted script to the /h/autoSaveDraft function.

CWE(s)
KEV Date Added
25 February 2025

Related Threats

Likely ATT&CK TechniquesAI

Techniques this vulnerability likely enables, inferred from its description, weakness type, and attributed-actor tradecraft. Confidence is per-technique.

T1189 Drive-by Compromise Initial Accessconfidence: HIGH
XSS in /h/autoSaveDraft allows script injection via crafted content that executes in other users' sessions.
T1059.007 JavaScript Executionconfidence: MEDIUM
Injected script runs in the victim's browser context, enabling JavaScript execution.
T1185 Browser Session Hijacking Collectionconfidence: MEDIUM
XSS can hijack authenticated browser sessions and capture or abuse session data.
inferred from description + CWE · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2023-37580Same product: Synacor Zimbra Collaboration Suiteboth on KEV
CVE-2022-27926Same product: Synacor Zimbra Collaboration Suiteboth on KEV
CVE-2018-6882Same product: Synacor Zimbra Collaboration Suiteboth on KEV
CVE-2023-43770Same product class: email / collaborationboth on KEV
CVE-2020-35730Same product class: email / collaborationboth on KEV
CVE-2023-5631Same product class: email / collaborationboth on KEV
CVE-2020-13965Same product class: email / collaborationboth on KEV
CVE-2023-47272Same product class: email / collaboration
CVE-2023-43102Same product class: email / collaboration
CVE-2023-43103Same product class: email / collaboration

Affected Assets

synacor
zimbra collaboration suite
8.8.15

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SI-10 Information Input Validation
  • SI-15 Information Output Filtering
  • SI-2 Flaw Remediation
Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)

Validate
Prove the fix (OWASP ASVS)
  • V1.1.2
  • V1.3.2

Mitigating Controls (NIST 800-53 r5) AI

prevent

Directly blocks the crafted script payload supplied to /h/autoSaveDraft by enforcing validation and sanitization of untrusted web input.

prevent

Filters or encodes dynamic content returned from the autoSaveDraft function so that injected scripts cannot execute in other users' browsers.

prevent

Requires prompt application of the vendor patch that eliminates the XSS flaw in the affected ZCS endpoint.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).

PR.PS-02 partial match
prevents

Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

detects

Secure-coding testing and automated code-analysis tools are applied to detect improper neutralization of script-related content during web-page generation.

prevents

Knowledge exchange on emerging attack techniques and patches reduces the likelihood that cross-site scripting flaws remain unaddressed in deployed applications.

prevents

Operational indicators of compromise for web-application attacks can be incorporated into WAF or input-filtering rules, lowering the likelihood that unsanitized data reaches the browser.

prevents

Requiring language-specific secure-coding standards and automated scanning during the SDLC catches missing output encoding or improper neutralization of untrusted data before the software reaches production.

prevents

Secure-coding standards, SAST scans and removal of insecure code samples together eliminate the failure to neutralize script content that produces cross-site scripting flaws.

none

Webpage malware scanning and block-listing of known malicious sites reduce the likelihood that reflected or stored script payloads reach a user’s browser.

References