curl 8.21.0

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Changes in 8.21.0 - June 24 2026

8.21.0 8.21.0 Changes:

• curl: named globs in output filename for upload glob references
• HTTP/3: add proxy CONNECT and MASQUE CONNECT-UDP support (ngtcp2 QUIC)
• http2: remove stream dependency tracking
• lib: drop support for CURLAUTH_DIGEST_IE
• libssh: add support for SHA256 host public keys
• tool_urlglob: add named globs Bugfixes:
• _ENVIRONMENT.md. Windows does case insensitive env variables
• _URL.md: remove the zone-id mention
• AmigaOS: curl_setup.h avoid explicit_bzero with clib2
• AmigaOS: fix build fallouts, re-add to CI
• asyn-thrdd: add IPv6 guards
• asyn-thrdd: fix result processing without wakeup socketpair
• autotools: mbedtls detection fixes
• BINDINGS: Update Hollywood link
• BUFQ.md: re-sync with source code
• build: enable -Wlogical-op picky warning for GCC 4.4+
• build: omit zlib pkg-config reference for Android
• cf-h2-prox: fix peer leak
• cf-h2-proxy: drop interim responses
• cf-https-connect: do not engage on proxy origin
• cf-ip-happy.c: minor comment typo
• cf-ip-happy: update documentation
• cf-socket: make Curl_addr2string static
• cf-socket: set scope_id for IPv6 link-local addresses
• cf-socket: store errno from do_connect in ctx->error
• cfilters: fix busy loop on blocked transfers
• chunked: reject invalid bytes in trailer
• CIPHERS.md: fix the example that uses only TLS 1.3
• cmake/FindGSS: drop "MIT Unknown" version value, related tidy ups
• cmake/FindGSS: drop CMake <3.16 compatibility logic
• cmake/FindGSS: fix comment, adjust custom flavor property name
• cmake/FindGSS: prioritize MIT over GNU in pkg-config detection
• cmake: auto-select static nghttp2/nghttp3/ngtcp2 Config
• cmake: export/forward NGTCP2_CRYPTO_BACKEND
• cmake: fix three issues generating lib options in config files
• cmake: fix zstd CMake config name
• cmake: opt in MSVC_VERSION 1951 to picky warnings
• cmake: quote COMPONENTS string in curl-config.in.cmake
• cmake: simplify LINK_ONLY imported target extraction
• config2setopts: use default protocol properly
• connect: remove deref of freed pointer in trace call
• content_encoding: fix limit failure message
• content_encoding: fix non-last chunked rejection
• content_encoding: timeout during slow decoding
• cookie: check __Secure- and __Host- case sensitively when read from file
• cookie: compare path case sensitively
• cookie: reject control octets in file-loaded cookies
• cookie: simplify strstore(), remove outdated comment
• cookie: tailmatch the domains for secure override
• cookie: trim trailing dots when checking PSL
• creds: add sasl service name
• creds: create with empty user+pass
• creds: mask OAuth bearer token in trace logs
• creds: remove two unused functions
• curl_easy_pause.md: rephrase the stream cache when pause clause
• curl_easy_setopt.md: change options when no transfer runs
• curl_formdata: fix to pass long where missing, document CURLFORM_NAMELENGTH
• curl_multi_assign.md: clarify lifetime
• curl_ntlm_core: fix nettle 4+ builds in certain MultiSSL combos
• curl_ntlm_core: propagate DES CryptEncrypt() error
• curl_sha512_256: fix result code on error
• CURLINFO_CONTENT_LENGTH_UPLOAD_T.md: expand
• CURLMOPT_SOCKETFUNCTION.md: this sends all file descriptors
• CURLOPT_CHUNK_BGN_FUNCTION: target is there for symlinks only
• CURLOPT_DISALLOW_USERNAME_IN_URL: is for CURLOPT_URL only
• CURLOPT_DOH_URL.md: does not inherit proxy options
• CURLOPT_ECH.md: simplify the description language
• CURLOPT_HAPROXYPROTOCOL.md: only sent for newly setup connections
• CURLOPT_MAXFILESIZE: clarify this also works for on-going transfers
• CURLOPT_PINNEDPUBLICKEY.md: does not apply for other origins
• CURLOPT_PORT.md: use stronger language
• CURLOPT_SHARE: warn about early remove
• CURLOPT_SSH_HOSTKEYFUNCTION.md: for new connections only
• CURLOPT_WRITEFUNCTION.md: mention redirects
• CURLOPT_WRITEFUNCTION.md: remove stray reference to HSTS
• delta: harden external command invocations
• digest: escape control codes too
• digest: flush proxy state on proxy or credential change
• digest: flush state on origin or credential change
• dns-httpsrr-lookup: use origin, not peer
• dnscache: remove Curl_dns_entry_link
• docs/libcurl: fix the version for curl_multi_socket_action
• docs: end "...can be used several times..." sentences with period
• docs: fix --follow doc typo
• docs: fix a couple of typos
• docs: fix grammar and wording in FAQ
• docs: fix odd wording in CONTRIBUTE.md
• docs: note CURLOPT_PINNEDPUBLICKEY has no effect on legacy LDAP backend
• docs: returned header size reflects HTTP/1-style format
• doh: cap the maximum TTL to 24 hours
• doh: stricter HTTPS RNAME parsing
• ECH: cleanups
• event: fix wakeup consumption
• ftp: avoid accessing EPSV response one byte past the NULL
• ftp: remove 2 Curl_resolv_blocking() calls
• ftp: remove bits.ftp_use_control_ssl
• ftplistparser: clear strings.target if not symlink
• gnutls: allow building with nettle 4.0
• gnutls: fix more nettle 4+ compatibility issues
• gnutls: require 3.7.2 for earlydata
• gsasl: fix potential double free
• gtls: fix ignored return and uninitialized status in OCSP check
• gtls: fix some typos
• gtls: minor fixes and improvements
• gtls: use the correct return code in trace output
• gtls: verify OCSP response signature in gtls_verify_ocsp_status
• h3-proxy: fix callback return values, and a typo in tests
• hostip: remove unused MAX_HOSTCACHE_LEN and MAX_DNS_CACHE_SIZE
• hsts.md: mention multiple curl invokes effect
• hsts: duplicate live HSTS data in curl_easy_duphandle
• http-proxy: verify CONNECT response headers
• HTTP3.md: update quiche build
• http: don't pass on set cookies to new origins
• http: prefer chunked encoding over Content-Length: 0
• http: reject spurious CR bytes in headers
• http_digest: return better error
• idn: replace header guards with forward declaration
• INSTALL-CMAKE.md: document CMake environment variables
• INTERNALS.md: document minimum nghttp3 and ngtcp2 versions
• KNOWN_BUGS.md: remove fixed GnuTLS <-> OpenSSL incompat bug
• KNOWN_BUGS: remove stale Threads::Threads entry
• krb5_sspi: fix error message on DecryptMessage() fail
• ldap: base64 encode binary LDIF values with WinLDAP
• ldap: fix minor leak on write callback error
• ldap: fix to not leak attribute on OOM (WinLDAP)
• ldap: switch off chasing referrals
• lib678: fix to not be perma-skipped
• lib: make __STDC_VERSION__ literals L (where missing)
• lib: transfer origin and proxy handling
• lib: two minor typos
• libcurl-easy.md: minor clarifications
• libssh2: do not use deprecated macros when unavailable
• libssh2: drop stray double-negative from strncmp() result
• libssh2: fix to return error code on missing parameter
• libssh2: replace macro names with non-misspelled alternatives
• libssh2: save non-standard port to known_hosts
• libssh2: sync version check with INTERNALS.md
• libssh2: use non-deprecated libssh2_knownhost_addc()
• libssh: map SSH_KNOWN_HOSTS_OTHER to CURLKHMATCH_MISMATCH
• m4: drop redundant conditions in TLS library detections
• Makefile.am: drop test1190 listed twice
• managen: apply minor fixes and improvements
• mbedtls: null-terminate the private key blob
• mk-unity.pl: #include, and not concatenate input headers
• mqtt: return error on truncated Remaining Length
• mqtt: validate PINGRESP and DISCONNECT have remaining_length == 0
• multi: handle pause in multi socket callback
• multi: remove a stale comment
• multi: silence gcc 16 -Wnull-dereference, bump CI job to test
• multi: xfers_really_alive
• netrc: remember and check filename loaded
• netrc: scanner refactor
• ngtcp2: fail handshake directly
• openssl: do not mix OpenSSL int result with CURLcode variable
• os400sys: fix theoretical length overflows
• peer.h: fix typo in comment
• pingpong: reject nul byte in server response line
• progress: fix CURLINFO time reporting
• psl: require libpsl 0.16.0 (2016-12-10) or greater
• pytest: pass --disable to curl
• pytest: re-enable test test_05_01 and test_05_02 for quiche 0.29.0+
• pythonlint.sh: make it fail on error, fix ruff warnings in pytest
• quic: count zero length packets against max
• ratelimits: use minimal burst rate
• RELEASE-PROCEDURE.md: update coming release dates
• resolve: mention in error that IP address is expected
• rtsp: bump buf after rtsp_filter_rtp()
• runner.pm: apply minor correctness fix
• runner.pm: set CURL_TESTNUM for precheck commands
• runtests: fix tests for curl builds with embedded CA bundle
• rustls: error on CURLOPT_CRLFILE with native CA store
• schannel: check schannel_sha256sum() success, and more
• schannel: enforce Extended Key Usage for custom CA roots
• schannel: error on TLS 1.3-only with cipher list
• schannel: fix https proxy for client cert and certinfo
• schannel: fix revoke_best_effort setting for proxy
• schannel: use fopen instead CreateFile
• schannel_verify: avoid out of blob access
• schannel_verify: simplify CryptQueryObject use
• scripts: catch Credits-to contributors
• SECURITY-ADVISORY.md: expand
• setopt: changing the proxy port is also a proxy change
• setopt: clear proxy auth properly on NULL
• setopt: clear the "custom" CA booleans when set to NULL
• setopt: CURLOPT_MAXCONNECTS set to 0 restores default value
• setopt: defref the old referer when setting a new
• setopt: fix to honor CURLOPT_PROXY_CAINFO_BLOB over Native CA
• setopt: gate a few proxy TLS options by checking backend support
• setopt: more careful cleanup of the HSTS cache
• setopt: return error if received curl_blob->data is NULL
• show-headers.md: mention bold headers and --no-styled-output
• sigv4: URL encode the username in the header
• smb: constify strchr() result variable
• smb: integer overflow proof a size check
• smbserver: update internal id generation for Python 3
• socket: introduce SOCK_EAGAIN() and use it
• socket: use name sockerr for socket error variables
• socks_sspi: invalid response length is a fatal error
• socks_sspi: store socks5_gssapi_enctype
• spnego_sspi: honor CURLOPT_GSSAPI_DELEGATION for Windows SSPI
• spnego_sspi: preserve distinction btw policy-only and uncond delegation
• src: fix comment typos
• src: sync nghttp2 versions checks with current requirements
• ssl native_ca_store: always reinit
• SSLCERTS: document 8.19.0 default Native CA builds (Windows)
• sspi: clear SSPI credentials on AcquireCredentialsHandle failure
• sspi: free libcurl allocated memory with curlx_free
• telnet: drop an int cast no longer necessary
• telnet: drop redundant interim variables
• telnet: fix error message typos
• telnet: fix old copy-paste typo in variable name
• telnet: honor CURLOPT_TIMEOUT in send_telnet_data()
• test1588: use %TESTNUMBER, not hard-coded number
• test1981: explicitly set the locale
• tests: add cookies feature to some tests
• tests: add an assert to avoid IPC blocking
• tests: add the "--resolve" keyword to tests that lack it
• tests: fix unit1636 with --disable-progress-meter
• tftp: avoid the timeout calc if the timeout is crazy
• tftp: stricter option name checks
• tidy-up: add space around operators, where missing
• tidy-up: apply clang-format fixes
• tidy-up: drop stray casts for allocated pointers
• tidy-up: miscellaneous
• tls: fix incomplete mTLS config in conn reuse and session cache
• tls: wolfssl: fixes for PQC key shares
• tool: warn when --ssl and --ftp-ssl-control override each other
• tool_formparse.c: fix two minor comment typos
• tool_formparse: polish error message + make two functions static
• tool_formparse: tool2curlparts is no longer recursive
• tool_help: rectify a bad assert
• tool_operhlp: avoid NULL to %s
• tool_urlglob: avoid overflow at end of range
• tool_urlglob: better 'Duplicate glob name' position
• tool_urlglob: make globbing error reported for correct position …