---
cve: "CVE-2026-47321"
severity: "HIGH"
cvss: 7.5
epss: "0.3%"
vendor: "Apache Software Foundation"
kev: false
exploited: false
published: "2026-09-21 08:16:37"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-22T23:19:17+02:00"
---

# CVE-2026-47321

> 7.5 HIGH

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Keine | good |
| A Verfügbarkeit | Hoch | bad |

## Referenzen

- <https://lists.apache.org/thread/y7xj1bl8qo47p9bktb11hg5v6k1d4dyj>
- <http://www.openwall.com/lists/oss-security/2026/09/21/1>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-47321) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_