Deserialization in Zaproxy Zap-Extensions
CVE-2026-57527
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.
Vulnerability class: Insecure Deserialization
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (51.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Zaproxy Zap-Extensions — versions 0
Weakness classification (CWE)
References
- github.com/zaproxy/zap-extensions/commit/ac6c3f94d38505bc0facea286a4d3728044c6e… (patch)
- github.com/zaproxy/zap-extensions/pull/7481 (issue-tracking)
- github.com/zaproxy/zap-extensions/releases/tag/viewstate-v4 (release-notes)
- www.vulncheck.com/advisories/zap-viewstate-add-on-insecure-deserialization-via-… (third-party-advisory)
- www.zaproxy.org/blog/2026-06-24-java-deserialization-vulnerability-in-zap-views… (vendor-advisory, technical-description)
Frequently asked questions
- What is CVE-2026-57527?
- CVE-2026-57527 is a high-severity vulnerability in Zaproxy Zap-Extensions, classified under Deserialization of Untrusted Data. CVSS score: 8.8/10. Published 2026-06-26.
- How severe is CVE-2026-57527?
- High severity. CVSS v3 base score is 8.8 out of 10.