CVE-2026-63436
zt-zip: Path traversal in fluent API unpack
What happened?
zt-zip is a Java library that provides convenience methods for ZIP archive manipulation. Prior to 1.18.0, the Zips.get(zip).unpack().destination(outputDir).process() fluent API in src/main/java/org/zeroturnaround/zip/Zips.java constructs output files directly from ZIP entry names without applying the destination-boundary validation used by ZipUtil.unpack(...). A crafted entry containing parent-directory traversal can therefore write outside outputDir through both the normal copy branch and the ZipEntryTransformer branch. Applications that extract untrusted archives only through ZipUtil.unpack(...) are unaffected because that API already calls checkDestinationFileForTraversal. This issue is fixed in version 1.18.0.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| zt-zipzeroturnaround | affected: < 1.18.0 | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.
Sources and remediation references
- https://www.cve.org/CVERecord?id=CVE-2026-63436
- https://github.com/zeroturnaround/zt-zip/security/advisories/GHSA-52c6-99qm-3hqr
- https://github.com/zeroturnaround/zt-zip/pull/180
- https://github.com/zeroturnaround/zt-zip/commit/59a76ad576b0fcd50ea018e3608afb946c1492fd
- https://github.com/zeroturnaround/zt-zip/releases/tag/v1.18.0