zt-zip: Path traversal in fluent API unpack
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 1.18.0
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.18.0.
- Exploitation?/40Exploitation: unknown (data gap). No CISA SSVC exploitation rating yet
- Exposure?/25Exposure: unknown (data gap). No advisory context yet
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity6.1/10CVSS 6.1
- No patch0/5No signal
What would change the score
- Would score about 61 if added to CISA KEV
- Would score about 56 if CISA's SSVC rates exploitation active
- Would score about 28 if advisories confirm default setups are exposed
CVE-2026-63436 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.1 (medium) and affects zt-zip; fixed in 1.18.0.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 6/100 · provisional
- Fix
- Fixed in 1.18.0
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The zt-zip Java library's fluent unpack API (Zips.get(...).unpack()...process()) can be tricked by a specially crafted ZIP archive into writing files outside the intended destination folder, which could overwrite or plant files elsewhere on the system. Applications that only extract archives through the library's ZipUtil.unpack method are not affected.
Read the original description
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.
What to do
Upgrade to a fixed version: 1.18.0.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- zeroturnaround zt-zip
fixed in 1.18.0
Evidence 4
- Advisory
- Repository
- Repository
- Repository
Corrections
None so far.
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Questions about CVE-2026-63436
Is CVE-2026-63436 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-63436?
zt-zip: before 1.18.0.Source: cve.now feed data
How do I fix CVE-2026-63436?
Upgrade to a fixed version: 1.18.0.Source: cve.now feed data