CVE-2026-57527

High

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.

SeverityHigh

CVSS8.8

Exploit probability—

ProductZaproxy Zap-extensions

PublishedJun 26, 2026

First seenJun 26, 2026

Weakness typeCWE-502Deserialization of untrusted data

How to fix

Update

zaproxy zap-extensions4 or later

Patches

github.com/zaproxy/zap-extensions/commit/ac6c3f94d38505bc0facea286a4d3728044c6e5c

Vendor advisories

Affected products

Product	Affected versions	Fixed in
zaproxy zap-extensions	v < 4	4

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