Pending RELEASE-NOTES for the upcoming release

This is work in progress and seeing changes before the release goes public on 2026-09-02.

Changes:

• gssapi: add support for Apple GSS Framework
• hardening: add API guards
• RFC 9421 HTTP Message Signatures support
• spnego: block NTLM fallback in SPNEGO negotiation
• TLS: drop support for TLS-SRP
• vquic: add option to use Apple fast UDP

Bugfixes:

• asyn-thrdd: retry link-local ipv6 if missing scope id
• autotools: minor fixes and improvements
• build: always use local `inet_pton()`/`inet_ntop()` implementations
• build: assume POSIX `select()` is available
• build: clear `Require.private` for static-only builds in `libcurl.pc`
• build: drop superfluous `STDC_HEADERS` macro
• build: enable thread-safe `getaddrinfo()` for OpenBSD
• build: minor debug option message fixes/improvements
• build: require `!NDEBUG` for debug-enabled (aka development) builds
• build: strip duplicate spaces after `Libs.private:` in `libcurl.pc`
• build: strip trailing spaces from `libcurl.pc`
• cd2nroff: fix backslashes for 4-space indent lines
• cd2nroff: stricter checks for asterisks for italics
• cf-ngtcp2-cmn: de-duplicate `ngtcp2_conn_client_new()` call code
• cf-ngtcp2-cmn: initialize new callback ptr for ngtcp2 1.24.0+
• cf-socket: disable TCP SYN retransmissions for localhost on Windows
• cfilters: fix event-based connection shutdown
• cmake: dedupe expressions into local vars in `cmake_uninstall.in.cmake`
• cmake: fix not to build `tunits` when `BUILD_CURL_EXE=OFF`
• cmake: flatten build tree, tidy up base dir variables
• cmake: minor improvements to `cmake_uninstall.in.cmake`
• cmake: replace `remove` command with `rm` and pass arg safely
• cmake: robustify base path in local file reference
• cmake: stop probing unused `float.h` for `STDC_HEADERS`
• cmake: use built-in variable and target property dump functions with CMake 4.5+
• configure: clarify --enable-debug option
• configure: fix misleading error messages
• configure: link `-lcrypt32` instead of `-lm` for wolfSSL on Windows
• configure: only check in the watt library if WATT_ROOT is set
• configure: remove double check for GnuTLS
• configure: set ldap lib to no by default for non-finds
• conncache: apply multi limits to transfers using a shared pool
• conncache: conn upkeep/alive: move and enhance
• conncache: connection alive checks intervals
• conncache: don't assume curl_off_t increment wrap-around
• connect: connection close tweaks
• content_encoding: exact-match the identity transfer-coding token
• content_encoding: give a clear error on multi-member gzip
• cookie: refuse to load cookies set against a PSL domain
• CREDENTIALS.md: remove comment about empty user/pass
• ctype: exclude control bytes from ISPRINT and ISGRAPH
• curl: help category cleanups
• curl_gssapi: document/update feature availability
• curl_trc: remove unused expire timers
• curl_url_set.md: expand the CURLU_NO_AUTHORITY description
• curl_ws_meta.md: polish and better vocabulary
• CURLOPT_HEADERFUNCTION.md: document folded header unfolding
• CURLOPT_SSH_*_KEYFILE: used for setting up, then no more
• CURLOPT_UNRESTRICTED_AUTH.md: 'Authorization', not 'Authentication'
• CURLSHOPT_(UN)SHARE.md: do not modify shares while in use
• DEPRECATE.md: HTTP/2 Server Push gets removed in March 2027
• dict: avoid busy-loop in sendf() when the socket is not writable
• dnsd: fix bounds check in `read_https_alpn_part()`
• docs/INTERNALS.md -> docs/DEPENDENCIES.md
• DoH: improvements
• FTP: fix TLS session reuse on the data connection
• ftp: reject control bytes in ACCT and alternative-to-user
• gitignore: maintenance updates
• gopher: reject CR and LF in the selector
• h2: bootstrap max streams from multi handle if in use
• h3-proxy: fix NULL deref when non-:status header arrives before :status
• header api: add guards
• HISTORY: add when c-ares support was introduced (2004)
• hostip: only cache negative resolves for authoritative answers
• http2: make server push transfers inherit share from parent
• http: avoid length underflow in Curl_compareheader
• http: fix non-tunneling proxy hostname use
• http: stop dropping large custom headers
• http: trim custom header name before the Authorization drop
• httpsrr: DoH with HTTPS, fix response handling
• idn: restore `MultiByteToWideChar()` `MB_ERR_INVALID_CHARS` flag
• INSTALL.md: add building-from-source overview section
• INTERNALS.md: require quiche 0.20.0+
• keylog: add a random size argument to Curl_tls_keylog_write()
• ldap: reject control characters in URL-decoded filter values
• ldap: support empty username and password
• ldap: support insecure mode for Windows native LDAP
• lib1587: fix gcc `-Wconversion` with LibreSSL on Windows, test in CI
• lib2405: adjust for non-threaded builds
• lib: add "Curl_" prefix to two global functions
• lib: add multi_wakeup_internal
• lib: fix 'ns' -> 'us' in trace messages
• lib: ratelimit timestamps
• lib: update mentions of the legacy "sessionhandle"
• libcurl.pc: add `License` tag
• libcurl.pc: add Copyright tag to the pkgconf file
• libcurl.pc: add the Link.ABI and Source tags
• mbedtls: enforce verifyhost when verifypeer is disabled
• mbedtls: replace `memset()` with `psa_hash_operation_init()`
• md5: replace magic numbers with `MD5_DIGEST_LEN`
• mime.c: avoid integer overflow in base64 size calculation
• mime: reject CR and LF in mail part name and filename
• mod_curltest: fix compiler warnings
• mqtt: reject control bytes in the topic
• multi: forbid curl_easy_pause from within multi socket callback
• multi: hold timeout values in 'int' instead of 'long'
• multi: remove #if 0'ed code that uses old struct
• multi: use index list for expire timeouts
• multihandle: move two struct fields
• ngtcp2: clean up after ngtcp2 in `curl_global_cleanup`
• ngtcp2: let verify failures win over expiry processing errors
• openldap: handle Curl_sasl_continue() returns better
• openssl+sectrust: fix session reuse
• openssl+sectrust: move session verified set into result check
• openssl: drop unused pre-OpenSSL3 `ctx_option_t` typedef
• openssl: prefer modern API flavors for `EVP_MD_CTX` new/free
• openssl: replace stray legacy API variant with `EVP_DigestInit_ex()`
• progress: cleanup, less memory
• psl: update a comment to understandable English
• pytest: update two H3 tests for nghttp3 1.18.0+
• quiche: set the max field section size
• rtsp: refactor method handling and improve error checks
• runtests: allow comments in `setenv` section, merge sections in test433
• runtests: fix `mode="warn"` tests passing unconditionally, fix test 1752
• runtests: flush cached test parts when (re)loading a file
• runtests: restore `-k` option and actively process as no-op
• sasl: fix zero-length response encoding
• schannel: fix error check logic in `get_client_cert()` file reader
• schannel: reuse the send buffer
• schannel: shut off experimental TLS 1.3 support for Win 10
• scorecard: fix `max_upload` init value in `ul_parallel()`
• scripts/badwords.txt: do not recommend using 'will' in rewrites
• scripts: replace/extend `--` with `--end-of-options` in git commands
• scripts: use end-of-options marker in `cd`, `mkdir`, `mv`, `sha256sum` commands
• servers: fix HANDLE leak in UWP builds
• servers: fix to reverse `SA_RESTART` option for `sigaction()` on modern codepath
• setopt: error for CURLOPT_SHARE when easy handle is used
• setopt: return OK earlier for the deprecated h2 dep options
• smtp: reject CR and LF in the envelope address
• spacecheck: cap number of lines per file
• src: safely clear certain buffers
• sshserver.pl: bump an sshd config to use its modern name
• ssls: fix potential memory leak on import
• sws: allow connection-monitor to log all disconnects
• sws: log the exact closing reason better, to help debugging tests
• terminal: Enhance terminal size detection for multiple outputs
• test 1560: test RFC4291 style IPv6 IPv4-mapped addresses
• test1560: allow to build and run without LDAP support
• test798: force IPv4 to avoid cross-runner port aliasing
• test: adjust test_06_13 for 0100::/64 being blackholed
• tests: address mutable class vars and naive datetime in Python code
• tests: change whitespace and comments in Python test code
• tests: convert unit test 1396 and 1398 into libtests
• tests: fix the FTP check for unexpected RST
• tests: fix type promotion on 32-bit arches in http test code
• tests: fix typo in assert message in http test
• tests: improve exception handling in Python test code
• tests: remove test1701
• tests: simplify by removing unneeded Python code
• tests: skip test 311 for wolfSSL 5.9.2
• tests: target Python 3.8 as the minimum Python version
• tests: use simpler constructions in Python code
• thrdpool: retry failed thread starts while items wait
• thrdqueue: drop name strdups from Curl_thrdq_create
• tidy-up: `TEXT()` vs `_TEXT()` vs `_T()` use (Windows)
• tidy-up: comments, messages, formatting
• tidy-up: drop redundant includes
• tidy-up: fix Perl syntax and formatting nits
• tidy-up: minor code fixes and improvements
• tidy-up: typos, comment nits
• timeval: make `Curl_freq` variable static (Windows)
• tool: do not flush on out-null
• tool: fix memory use in parallel mode
• tool: init progress bar on demand
• tool: remove duplicate setopts
• tool_cb_hdr: de-duplicate filename setter
• tool_cb_prg: avoid integer overflows
• tool_doswin: add stdin relay auth
• tool_operate: limit `is_using_schannel()` call to Windows
• tool_operate: only check for schannel if on windows
• tool_operate: remove call to abort()
• tool_xattr: add support for Windows alternate data stream
• typecheck-gcc: allow passing `char[]` as callback data
• uint-bset: add slot0 member
• uint-spbset: reused empty chunks
• unit3214: fix to pass on systems with >=128-bit pointers
• url: fix negotiate/ntlm connection reuse
• url: reject control codes in credentials set via CURLOPT
• urlapi: allow URLs to not have userauth (hostname)
• urlapi: avoid dedotdotify() if possible
• urlapi: clear password buffer on error path
• urlapi: do not keep an internal port string
• urlapi: improved return codes
• urlapi: preserve empty markers in relative URLs
• vms: fix symbol typo and missing closing quotes in `config_h.com`
• vquic: add Curl_ prefix to some global functions
• vquic: initialize new callback slot for nghttp3 v1.18.0+
• vquic: silence `-Wmissing-field-initializers` for nghttp3/ngtcp2 callback tables
• vquic: use ngtcp2 v1.25.0 new close2 callback
• vssh: keyfile use cleanups
• VULN-DISCLOSURE-POLICY.md: issues that should be found by tests are LOW
• websocket: pause writing and meta data fix
• wolfssl: fix build for wolfssl without bio chain support
• ws: pause/unpause write handling

Contributors:

11soda11, 1rhino2 on hackerone, AlanKingPL, Alb3e3, Alhuda Khan, anupamme, Bartel Sielski, Bigtang on hackerone, Bill Mill, Bryan Henderson, Carlos Henrique Lima Melara, CatboxParadox, Christian Ullrich, Christoph Reiter, claudex on github, Collin Funk, Dan Fandrich, Daniel Gustafsson, Daniel Stenberg, dependabot[bot], ed0d2b2ce19451f2 on github, Emmanuel Ugwu, Eunsoo Kim, firexinghe on github, Graham Campbell, Hendrik Hübner, HwangRock, itzTanos29, Joel Depooter, Johannes Schindelin, Keng-Yu Lin, kit-ty-kate on github, Laurent Sabourin, Marcel Jamin, Martin Dukek, Matthew John Cheetham, Max Dymond, Memduh Çelik, Patrick Monnerat, Pavel Sobolev, pszemus on github, Ralf Mueller, Ramesh Adhikari, Ray Satiro, renovate[bot], Rito Rhymes, RMMoreton on github, Roger Leigh, Ross Burton, Sameeh Jubran, Sam James, Samuel Dainard, Sergei Zimmerman, smaeljaish on hackerone, Stefan Eissing, Stephan Zeisberg, stze on hackerone, Thomas Chauchefoin, Viktor Szakats, xmoezzz on github, Yoshiro Yoneya