GHSA-mfg7-5gfp-c4w3

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GHSA-mfg7-5gfp-c4w3

Summary: Netty: Memory Leak in DNS Record Decoder via Malformed Domain Names

Details: ### Summary A memory leak can be caused in Netty's DNS codec by sending malicious DNS packets containing invalid domain names. Because the leak occurs incrementally per packet, sustained malicious requests will cause a gradual Denial of Service. ### Details Inside `io.netty.handler.codec.dns.AbstractDnsRecord`, the parsed domain name string is passed to `IDN.toASCII(name)`. If the domain name contains characters that violate IDNA rules, `IDN.toASCII` throws an `IllegalArgumentException`. Because this exception occurs inside the constructor before the `DnsRecord` instance can assign the buffer to its content field for later release, the ByteBuf whose reference count was incremented (or newly allocated) is never released, resulting in a direct memory leak. There are several places where variants of this leak happen: - `io.netty.handler.codec.dns.DefaultDnsRecordDecoder#decodeRecord(java.lang.String, io.netty.handler.codec.dns.DnsRecordType, int, long, io.netty.buffer.ByteBuf, int, int)` invokes `in.retainedDuplicate()` or creates a new buffer `out` when constructing `DefaultDnsRawRecord` - `io.netty.handler.codec.dns.DnsCodecUtil#decompressDomainName` allocates a new `ByteBuf` and passes it to `encodeDomainName()`. If the decompressed domain name contains a null byte (`\0`), `encodeDomainName()` throws an `IllegalArgumentException`, leaking the newly allocated buffer. ### Impact Resource Exhaustion. Any application utilizing Netty's DnsRecordDecoder (such as DnsNameResolver or custom DNS servers) is vulnerable.

References: https://github.com/netty/netty/security/advisories/GHSA-mfg7-5gfp-c4w3, https://github.com/netty/netty/pull/17063, https://github.com/netty/netty/pull/17065, https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b, https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6, https://github.com/netty/netty, https://github.com/netty/netty/releases/tag/netty-4.1.136.Final, https://github.com/netty/netty/releases/tag/netty-4.2.16.Final