Decompression bomb denial-of-service in Apache MINA CompressionFilter
CVSS 3.1
7.5high
EPSS
—
Published
()
Modified
AI analysis
CVE-2026-47321 is an unauthenticated remote denial-of-service vulnerability in the CompressionFilter class of the Apache MINA network application framework. The filter uses ZLib to inflate incoming compressed data but does not limit the resulting decompressed size, so an attacker can send a small, highly compressed payload (a 'zip bomb' with a compression ratio exceeding 1,000x) that expands to exhaust application memory and crash the service. Any application using MINA's CompressionFilter on a network-facing endpoint is affected until the developer configures a size limit. The fix introduces a configurable maximum decompressed size and compression-ratio limit, but applications must explicitly pass these limits via new constructor parameters or the fluent API. No public proof-of-concept is known, the issue is not in CISA's KEV catalog, and there are no confirmed reports of in-the-wild exploitation.
What to do: Upgrade Apache MINA to the release containing the fix and configure CompressionFilter with a maximum decompressed size, e.g. new CompressionFilter(compressInbound, compressOutbound, compressionLevel, maxDecompressedSize), optionally adding maxDecompressRatio and decompressRatioMinSize parameters or using the new fluent API (setMaxDecompressedSize, setMaxDecompressRatio, setDecompressRatioMinSize). Audit all code paths that instantiate CompressionFilter on network-facing endpoints, and apply limits that balance your expected payload sizes against memory-exhaustion risk. As an interim mitigation, disable or remove CompressionFilter from the filter chain where compressed transport is not required.
Affected
Apache MINA (CompressionFilter class using ZLib inflate)
versions prior to the release containing the maxDecompressedSize fix; no specific version numbers provided in the data — applications must pass the new construc
Estimated exposure
largelikely on the order of hundreds of thousands of deployments (widely embedded Java network framework) — Apache MINA is a popular, long-established Java NIO framework embedded in many server products and custom applications, but only applications that enable CompressionFilter are vulnerable, so the true exposed count is an order-of-magnitude…
Description
The CompressionFilter class uses ZLib to deflate and inflate data sent and received. When we inflate incoming data, the filter does not control the resulting size, and create a buffer no matter what. Some compressed data may have a compression ration greater than 1 thousand, leading to an exhaustion of the application memory, as we don't control the deflated size. The fix adds such a control by allowing the application developer to provide a fixed size limit, which when reached throws an exception. It also allows the user to provide a compression ratio that should not be exceeded, protected the application from small inflated files that inflate in gigantic files, but with a grace limit for the resulting size (1Mb) to avoid false positive (like a very small file inflating with a high ratio, but resulting with a acceptable size, like a few thousands bytes) For application using this feature, it is highly recommended to create the CompressionFilter and to pass the maximum limit as a forth constructor parameter, maxDecompressedSize: public CompressionFilter(final boolean compressInbound, final boolean compressOutbound, final int compressionLevel, final int maxDecompressedSize)Optionally one can also provide a maxDecompressRatio fifth parameter, and a decompressRatioMinSize sixth parameter to allow small inflated files with a high compression ratio to still be accepted. Here are the additional constructor: public CompressionFilter(final boolean compressInbound, final boolean compressOutbound, final int compressionLevel, final int maxDecompressedSize, final long maxDecompressRatio, final long decompressRatioMinSize) Also note that a fluent API has been added to spare the users the pain to call a constructor with that many parameters: CompressionFilter compressionFilter = new CompressionFilter() .setCompressionLevel(Zlib.COMPRESSION_MAX) .setMaxDecompressedSize(1_000_000) .setMaxDecompressRatio(100). .setDecompressRatioMinSize(100_000); Applications using Apache MINA are advised to upgrade and configure their CompressionFilter instance.
Apache MINA CompressionFilter allows unbounded zlib inflation, enabling a decompression-amplification denial of service.
CVE-2026-47321 is an unbounded decompression flaw in Apache MINA's mina-filter-compression component. CompressionFilter uses Zlib to inflate incoming data but does not limit the resulting size, allowing a decompression-amplification denial of service. Affected versions are 2.2.0 before 2.2.8, 2.1.0 before 2.1.13, and 2.0.0 before 2.0.29. The oss-security post does not report exploitation in the wild.