CVE-2026-32731: ApostropheCMS has Arbitrary File Write (Zip Slip / Path Traversal) in Import-Export Gzip Extraction

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.6%, percentile 49: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 49% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes @apostrophecms/import-export (npm) <= 3.5.2, fixed in 3.5.3. Check your lockfile, including transitive dependencies.

What it is

ApostropheCMS is an open-source content management framework. Prior to version 3.5.3 of @apostrophecms/import-export, The extract() function in gzip.js constructs file-write paths using fs.createWriteStream(path.join(exportPath, header.name)). path.join() does not resolve or sanitise traversal segments such as ../. It concatenates them as-is, meaning a tar entry named ../../evil.js resolves to a path outside the intended extraction directory. No canonical-path check is performed before the write stream is opened. This is a textbook Zip Slip vulnerability. Any user who has been granted the Global Content Modify permission — a role routinely assigned to content editors and site managers — can upload a crafted .tar.gz file through the standard CMS import UI and write attacker-controlled content to any path the Node.js process can reach on the host filesystem. Version 3.5.3 of @apostrophecms/import-export fixes the issue.

From the GitHub advisory

Reported: 2026-03-08 Status: patched and released in version 3.5.3 of @apostrophecms/import-export

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Product

| Field | Value | |---|---| | Repository | apostrophecms/apostrophe (monorepo) | | Affected Package | @apostrophecms/import-export | | Affected File | packages/import-export/lib/formats/gzip.js | | Affected Function | extract(filepath, exportPath) — lines ~132–157 | | Minimum Required Permission | Global Content Modify (any editor-level user with import access) |

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Weakness type: CWE-22.

Product: @apostrophecms/import-export (npm) · Assigned by: GitHub_M · Published: 2026-03-18

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.61% probability of exploitation activity in the next 30 days; percentile 49.

Timeline

• 2026-03-18 — CVE record published by GitHub_M
• 2026-03-18 — GitHub-reviewed advisory GHSA-mwxc-m426-3f78 published (critical)
• 2026-03-19 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-mwxc-m426-3f78 github.com
2. CVE.org record CVE-2026-32731 cve.org
3. NVD entry CVE-2026-32731 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com

Critical npm advisories · Today’s Security Digest