What’s Vulnerable › Vulnerabilities

CVE-2026-57527: ZAP ViewState Add-on Insecure Deserialization via JSFViewState.decode()

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-26 · updated 2026-10-25
• Weakness: CWE-502

Description

Zed Attack Proxy (ZAP) ViewState add-on before version 4 contains an insecure deserialization vulnerability that allows attackers who control a proxied web server to achieve arbitrary code execution by embedding a malicious serialized Java object in the javax.faces.ViewState HTTP response parameter. The JSFViewState.decode() method base64-decodes the ViewState value and passes it directly to ObjectInputStream.readObject() without a deserialization filter, allowlist, or type restriction, causing the malicious object to be deserialized within the ZAP JVM when the Desktop UI renders the ViewState panel.

Affected products

• zaproxy zap-extensions: before 4 — fixed in 4

How to fix

Upgrade to a fixed version: zaproxy zap-extensions 4. Check the vendor advisory for mitigations.

References

• https://github.com/zaproxy/zap-extensions/commit/ac6c3f94d38505bc0facea286a4d3728044c6e5c
• https://github.com/zaproxy/zap-extensions/pull/7481
• https://github.com/zaproxy/zap-extensions/releases/tag/viewstate-v4
• https://www.vulncheck.com/advisories/zap-viewstate-add-on-insecure-deserialization-via-jsfviewstate-decode
• https://www.zaproxy.org/blog/2026-06-24-java-deserialization-vulnerability-in-zap-viewstate-addon/

Get alerted when CVE-2026-57527 or the next vulnerability affects your stack