CVE-2026-57527 ZAP ViewState Add-on Insecure Deserialization via JSFViewState.decode()
Attackers controlling a proxied server can achieve arbitrary code execution in ZAP by sending malicious serialized Java objects in ViewState parameters.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-57527?
CVE-2026-57527 is a high-severity unsafe deserialization vulnerability in zaproxy zap-extensions, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-502
Which versions are affected by CVE-2026-57527?
How do I fix CVE-2026-57527?
No fix has been published for CVE-2026-57527 yet. Limit exposure of the affected software until one is available.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-57527 being exploited?
There is no known exploitation of CVE-2026-57527 in the wild and no public exploit code.
Sources
Also known as GHSA-grq4-7pwr-9rmp.