CVE-2026-39244 adm-zip: Crafted ZIP file triggers 4GB memory allocation
Attackers can crash applications using adm-zip by submitting small ZIP files with manipulated headers that trigger excessive memory allocation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-39244?
CVE-2026-39244 is a high-severity denial of service vulnerability in n/a, published on 10 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
adm-zip before 0.5.18 is vulnerable to denial of service via a crafted ZIP file with a manipulated uncompressed size header field. In zipEntry.js line 103, Buffer.alloc(_centralHeader.size) allocates memory based on the declared uncompressed size from the ZIP central directory header without validating it against the actual compressed data size or imposing any upper bound. The size value is read directly from the binary header at entryHeader.js line 266 with no bounds check. An attacker can craft a ~120-byte ZIP file that declares ~4GB uncompressed size, causing a memory allocation amplification ratio of over 33 million to 1. The allocation occurs before CRC validation, so the malicious payload cannot be rejected early. All extraction and read methods are affected: readFile(), readAsText(), extractEntryTo(), extractAllTo(), extractAllToAsync(), test(), and entry.getData(). Any application accepting untrusted ZIP files via adm-zip is vulnerable to immediate process crash.
Weakness: CWE-400
Which versions are affected by CVE-2026-39244?
2 open source packages ship an affected version, including adm-zip.
| Package | Affected | Fixed in |
|---|---|---|
adm-zip npm | All versions | 0.6.0 |
adm-zip npm | All versions | 0.6.0 |
How do I fix CVE-2026-39244?
Upgrade adm-zip to 0.6.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-39244 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39244 exists.
Sources
Also known as CLEANSTART-2026-CE47841, CLEANSTART-2026-OC57754, CLEANSTART-2026-ZL52542, CLSA-2026-1784856024, CLSA-2026-1790161376, CLSA-2026-1790162696 and 20 more.