CVE-2026-44890

Netty is a network application framework for development of protocol servers and clients. In netty-codec-redis prior to versions 4.1.135.Final and 4.2.15.Final, an attacker can cause DoS by sending crafted Redis payloads across multiple connections without \r\n. This exhausts the server's direct memory pool (OutOfDirectMemoryError), preventing legitimate connections from being processed. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

Summary

An attacker can cause DoS by sending crafted Redis payloads across multiple connections without \r\n. This exhausts the server's direct memory pool (OutOfDirectMemoryError), preventing legitimate connections from being processed.

Details

io.netty.handler.codec.redis.RedisDecoder decodes the length of bulk strings and array headers using the decodeLength method. This method reads bytes from the network until it encounters a \n character. However, it does not enforce any maximum length check while buffering the bytes if the \n character is not found. An attacker can exploit this by sending a continuous stream of digits (e.g., $1111...) without ever sending a \n.

To cause a true Denial of Service, an attacker must open multiple concurrent connections and distribute the unbounded payloads among them.

According to the RESP specification (https://redis.io/docs/latest/develop/reference/protocol-spec/), all parts of the protocol are strictly terminated with \r\n. Furthermore, the length prefix itself is an integer representation that must fit within standard numeric limits (e.g., a 64-bit signed integer). Therefore, a stream of digits exceeding these bounds without \r\n is a protocol violation and should be rejected immediately rather than buffered indefinitely.

Impact

Denial of Service due to memory exhaustion. Any application using Netty's RedisDecoder to handle untrusted Redis traffic is vulnerable.

A client might overload the server by issue frequent RST frames. This can cause a massive amount of load on the remote system and so cause a DDOS attack.

Impact

This is a DDOS attack, any http2 server is affected and so you should update as soon as possible.

Patches

This is patched in version 4.1.100.Final.

Workarounds

A user can limit the amount of RST frames that are accepted per connection over a timeframe manually using either an own Http2FrameListener implementation or an ChannelInboundHandler implementation (depending which http2 API is used).

References

• https://www.cve.org/CVERecord?id=CVE-2023-44487
• https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/
• https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-above-398-million-rps/

Red Hat Lightwell has released io.netty:netty-codec-redis 4.1.100.Final-rhlw-00001 with backported fixes for CVE-2026-42586, CVE-2026-44250, CVE-2026-44890, CVE-2026-48006, CVE-2026-50011, and CVE-2026-56818.

CVE-2026-42586: Netty: CRLF Injection in Netty Redis Codec Encoder

CVE-2026-44250: Netty: Memory Exhaustion in RedisArrayAggregator due to Deeply Nested Arrays

CVE-2026-44890: Netty has Unbounded Direct Memory Consumption in its RedisDecoder

CVE-2026-48006: Netty's Lack of Lifecycle Cleanup Leads to Pooled ByteBuf Leak in RedisArrayAggregator

CVE-2026-50011: Netty has unbounded pre-allocation in RedisArrayAggregator from RESP array length

CVE-2026-56818: Netty: RedisArrayAggregator max-elements failure leaves retained partial aggregate state

This patched artifact is a drop-in replacement for io.netty:netty-codec-redis 4.1.100.Final from Maven Central.

Root has patched GHSA-xpw8-rcwv-8f8p in the io.root.io.netty:netty-codec-http2 package for Root:Maven. Multiple fixed versions available.

Netty is a network application framework for development of protocol servers and clients. In netty-codec-redis prior to versions 4.1.135.Final and 4.2.15.Final, an attacker can cause DoS by sending crafted Redis payloads across multiple connections without \r\n. This exhausts the server's direct memory pool (OutOfDirectMemoryError), preventing legitimate connections from being processed. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

TuxCare rebuilt 5 io.netty packages to address 5 CVEs. Fixed in 4.1.92.Final-tuxcare.4.

TuxCare rebuilt 4 io.netty packages to address 5 CVEs. Fixed in 4.1.117.Final-tuxcare.1.

TuxCare rebuilt 7 io.netty packages to address 11 CVEs. Fixed in 4.1.130.Final-tuxcare.1.

TuxCare rebuilt 2 io.netty packages to address 2 CVEs. Fixed in 4.1.75.Final-tuxcare.3.

TuxCare rebuilt 2 io.netty packages to address 2 CVEs. Fixed in 4.1.73.Final-tuxcare.2.

TuxCare rebuilt io.netty:netty-codec-redis to address 1 CVE. Fixed in 4.1.82.Final-tuxcare.4.

TuxCare rebuilt 8 io.netty packages to address 13 CVEs. Fixed in 4.1.115.Final-tuxcare.7.

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TuxCare rebuilt 47 io.netty packages to address 62 CVEs. Fixed in 4.1.94.Final-tuxcare.1.

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TuxCare rebuilt 46 io.netty packages to address 19 CVEs. Fixed in 4.1.80.Final-tuxcare.1.

TuxCare rebuilt 7 io.netty packages to address 15 CVEs. Fixed in 4.1.101.Final-tuxcare.1.

TuxCare rebuilt 47 io.netty packages to address 19 CVEs. Fixed in 4.1.96.Final-tuxcare.1.

TuxCare rebuilt 7 io.netty packages to address 13 CVEs. Fixed in 4.1.100.Final-tuxcare.1.

TuxCare rebuilt 8 io.netty packages to address 17 CVEs. Fixed in 4.1.128.Final-tuxcare.1.

TuxCare rebuilt 15 io.netty packages to address 27 CVEs. Fixed in 4.1.72.Final-tuxcare.1.

TuxCare rebuilt 43 io.netty packages to address 25 CVEs. Fixed in 4.1.68.Final-tuxcare.1.

TuxCare rebuilt 14 io.netty packages to address 26 CVEs. Fixed in 4.1.118.Final-tuxcare.1.

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TuxCare rebuilt 7 io.netty packages to address 13 CVEs. Fixed in 4.1.51.Final-tuxcare.2.

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TuxCare rebuilt 40 io.netty packages to address 5 CVEs. Fixed in 4.1.52.Final-tuxcare.5.

TuxCare rebuilt 5 io.netty packages to address 11 CVEs. Fixed in 4.1.42.Final-tuxcare.4.

TuxCare rebuilt 7 io.netty packages to address 16 CVEs. Fixed in 4.1.38.Final-tuxcare.2.