CVE-2026-122146101arrowz fflate uncontrolled resource consumption
CVE-2026-122146 is a uncontrolled resource consumption in 101arrowz fflate, rated medium (5.5 on CVSS 4.0).
Why this priority: A public proof of concept exists and exploitation can be automated.
Published · Updated · NVD status: Deferred
What it is
Requests can consume unbounded CPU, memory or connections and starve the service. A size taken from input makes the software try to allocate huge amounts of memory.
How it is reached
An attacker can exploit it over the network, without an account, and nobody has to click anything.
What an attacker gains
The direct impact is limited: partial access to data or a partial outage. In practice, this kind of flaw lets an attacker exhaust CPU, memory or connections until the service stops answering.
Is it being exploited?
CISA's SSVC assessment notes a public proof of concept. It can be exploited automatically, at scale. EPSS estimates a 0.29% chance of exploitation activity in the next 30 days, higher than 22% of scored CVEs.
What to do
- No fixed version is listed yet. Find every place 101arrowz fflate runs, watch the references for a fix, and plan a replacement if it is no longer supported.
- While there is no fix, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
Description from NVD
A weakness has been identified in 101arrowz fflate up to 0.8.3. This issue affects the function unzipSync of the file esm/index.mjs. This manipulation causes uncontrolled memory allocation. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be used for attacks. It is suggested to update the configuration settings. The maintainer disputes this issue as a vulnerability. The library is a pure JavaScript decompressor that allocates memory proportional to the decompressed payload size, which is expected behavior. Excessive allocations simply throw a standard JavaScript RangeError or reach engine heap limits. Furthermore, because a low-level decompression library cannot distinguish between a maliciously crafted compression bomb and a legitimate file with a high compression ratio, the API explicitly provides a filter option allowing callers to restrict decompressed file sizes and prevent denial-of-service according to their application's requirements, as seen both in the documentation and noted in the reported issue.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Public entry points and shared services that must stay up. The flaw sits between untrusted traffic and shared capacity.
Trust boundaries in play
- Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
- Between untrusted traffic and shared capacity. An attacker who crosses it can exhaust CPU, memory or connections until the service stops answering.
Questions to answer about your own systems
- Where does 101arrowz fflate run in your systems, and at which version?
- Which of those instances can be reached from the internet or partner networks?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.