RELEASE NOTES: JDK 21.0.10

Changes to the Default Time Zone Detection on Debian-based Linux

On Debian-based Linux distributions such as Ubuntu, the /etc/timezone file was previously used to determine the JDK's default time zone (TimeZone.getDefault()). According to Debian's Wiki, /etc/localtime is now the primary source for the system's default time zone, making /etc/timezone redundant. As a result, the JDK's default time zone detection logic has been updated to use /etc/localtime instead of /etc/timezone. If /etc/localtime and /etc/timezone are inconsistent for any reason, the JDK's default time zone is now determined solely based on /etc/localtime file.

`Files.readString` May Return Incorrect String When Using UTF-16 or Other Charsets

Strings read with java.nio.files.Files.readString may return incorrect strings when decoding with a charset other than US-ASCII, ISO08859-1, or UTF-8. Reading strings with other multi-byte charsets, such as UTF_16, may produce incorrect results.

As a work-around, disable compact strings by setting -XX:-CompactStrings on the command line.

This issue will be fixed in a future update.

Disabled TLS_RSA Cipher Suites

The TLSRSA cipher suites have been disabled by default, by adding "TLSRSA_" to the jdk.tls.disabledAlgorithms security property in the java.security configuration file. The TLSRSA cipher suites do not preserve forward-secrecy and are not commonly used. Some TLSRSA cipher suites are already disabled because they use DES, 3DES, RC4, or NULL, which are disabled. This action disables all remaining TLSRSA cipher suites. Any attempts to use cipher suites starting with "TLSRSA" will fail with an SSLHandshakeException. Users can, at their own risk, re-enable these cipher suites by removing "TLSRSA_" from the jdk.tls.disabledAlgorithms security property. The following previously enabled cipher suites are now disabled:

TLS_RSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_128_GCM_SHA256
TLS_RSA_WITH_AES_256_CBC_SHA256
TLS_RSA_WITH_AES_128_CBC_SHA256
TLS_RSA_WITH_AES_256_CBC_SHA
TLS_RSA_WITH_AES_128_CBC_SHA

Disabled SHA-1 in TLS 1.2 and DTLS 1.2 Handshake Signatures

The SHA-1 algorithm has been disabled by default in TLS 1.2 and DTLS 1.2 handshake signatures, by adding "rsa_pkcs1_sha1 usage HandshakeSignature, ecdsa_sha1 usage HandshakeSignature, dsa_sha1 usage HandshakeSignature" to the jdk.tls.disabledAlgorithms security property in the java.security config file. RFC 9155 deprecates the use of SHA-1 in TLS 1.2 and DTLS 1.2 digital signatures. Users can, at their own risk, re-enable the SHA-1 algorithm in TLS 1.2 and DTLS 1.2 handshake signatures by removing "rsa_pkcs1_sha1 usage HandshakeSignature, ecdsa_sha1 usage HandshakeSignature, dsa_sha1 usage HandshakeSignature" from the jdk.tls.disabledAlgorithms security property.