Vulnerability · Published Nov 3, 2026 · Assigned by GitHub_M

CVE-2026-63499zt-zip: ZipUtil.unpack can change file permissions of output directory

Medium 6.9

In plain English

A medium-severity security flaw in zt-zip from zeroturnaround. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).

Severity (CVSS 4.0)6.9Medium

Exploit odds (30 days)0.3%top 79.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

zt-zip is a Java library that provides convenience methods for ZIP archive manipulation. Prior to 1.18.1, ZipUtil.unpack(...) can apply stored ZIP-entry permissions to the extraction output directory when an entry name such as / or ./ resolves to that directory itself. Because the path traversal checks permit self-referencing entries that do not escape the destination, the unpacker's permission-handling path can replace restrictive output-directory permissions with attacker-supplied permissions. This affects applications that unpack untrusted ZIP files, and POSIX systems demonstrate the issue directly, while ZTFilePermissionsUtil.fetchDefaultStrategy provides fallback permission handling on other supported systems. This issue is fixed in version 1.18.1.

Affected products (as reported)

Vendor	Product	Versions
zeroturnaround	zt-zip	< 1.18.1

Weakness: CWE-23 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

References

https://github.com/zeroturnaround/zt-zip/security/advisories/GHSA-v2g6-7r9j-v6px x_refsource_CONFIRM
https://github.com/zeroturnaround/zt-zip/pull/191 x_refsource_MISC
https://github.com/zeroturnaround/zt-zip/commit/1b625467b4c3cd3a9bee9efc35bdef2f8d9c8dad x_refsource_MISC
https://github.com/zeroturnaround/zt-zip/releases/tag/v1.18.1 x_refsource_MISC