OpenVPN 2.7.7 released

The OpenVPN community project team is proud to release OpenVPN 2.7.7. This is a
bugfix release fixing several security issues.

Security fixes:

* reliability layer: avoid unbounded reliable TLS timeout, and ignore acks for
 packets that cannot be outstanding (CVE-2026-84732)
 Both reliability layer bugs found by Mark Bregman (Fox-IT)
* windows: fix CreateProcess() command line quoting for characters that are special
 to cmd.exe, where a combination of validation script plus rogue CA could lead to
 misbehavior (CVE-2026-84256)
 Bug found by Clouditera Security
* windows: fix tapctl to always call netsh.exe with full path (as we do elsewhere)
 (CVE-2026-84226)
 Bug found by BreachX Zero Day Labs (using Typhon AI Mil v2)
* windows: don't use NULL DACL with system objects, namely the --service exit event
 and the netsh.exe guard semaphore.
 The old approach was prone to a local DoS where one user could interfere with
 other users' openvpn processes by blocking the netsh semaphore or sending events.
 This only affects setups not using the iservice, or using the automatic service to
 start/stop openvpn (CVE-2026-82312)
 Bug found by DEBRAJ BASAK
* openvpnserv (windows): pass correct NRPT domains size - when IDN domains with UTF8
 encoding were involved, a buffer overread could be achieved (CVE-2026-78221)
 Bug found by BreachX Zero Day Labs (using Typhon AI Mil v2)
* openvpnserv (windows): don't allow '/' in config paths.
 The APIs windows uses for path validation do not handle '/' as path separator,
 while the file open APIs do, so this could be used to circumvent our config path
 validation, leading to openvpn.exe starting a user-controlled config file even if
 administratively not allowed (CVE-2026-78043)
 Bug found by BreachX Zero Day Labs (using Typhon AI Mil v2)
* dhcp (windows): fix off-by-one in write_dhcp_search_str() temp buffer guard -
 suitable DHCP options could lead to a single-byte overflow of a temp buffer
 (CVE-2026-81738)
 Bug found by Andre Kropp (Nexory) and ChinhNguyen
* linux netlink: validate netlink replies against the request
 Suggested by Joshua Rogers as a security improvement
* openvpnserv (windows): fix off-by-one on input validation (discovered while fixing
 CVE-2026-78221)
* openvpnserv (windows): harden CheckConfigPath() a bit more (another improvement
 while working on CVE-2026-78043)

User-visible Changes:

* when using EPOCH data channel format, reduce the number of future keys from 16 to
 4 - the previous calculation was wrong, and 4 spare keys are sufficient for 100+
 Gbit/s links. This means less log spam in userland and fewer resources used in
 in-kernel implementations.

Bugfixes:

* work around a pubkey-handling bug in mbedTLS 4.1.0 and 4.2.0 (supposedly fixed in
 4.3.0)
* multi: don't let stale-routes-check delete permanent routes - --stale-routes-check
 did not only delete dynamic cached routes, but also routes installed by --iroute
 and --ifconfig-push. Fixed by introducing route flags and restraining the check on
 them (Github: OpenVPN/openvpn#1063)
* ssl: do not queue control ciphertext while a packet is still queued (fixes problems
 in TCP p2p handshake when both sides try to handshake at the same time) (Github:
 OpenVPN/openvpn#1089)
* reenable xmit_hold when using p2p tcp-server and tls-server - in TCP server mode
 the server is not expected to initiate the TLS handshake. This was introduced by
 the multisocket code checking the wrong variable for socket protocol (Github:
 OpenVPN/openvpn#1089)
* clinat: do not adjust UDP checksum if zero (as per RFC768) (Github:
 OpenVPN/openvpn#1037)
* openssl: avoid resetting the HMAC key on every packet (Github:
 OpenVPN/openvpn#1088)
* openvpnserv (windows): fix log lines format string - interface names with
 international characters printed in some error messages need to be converted from
 UTF8 to UCS16 first.
* fix format string specifier for size_t (%zu)
* fix test_misc compile issues with -Werror

Windows MSI changes since 2.7.6-I001:

* Update included dco-win driver to v2.8.7
  * peer: fix use-after-free in multipeer peer table handling (Github: OpenVPN/ovpn-dco-win#140)
  * inf: set the device security descriptor in the hardware key (Github: OpenVPN/ovpn-dco-win#139)

More details can be found in the Changes document:

<https://github.com/OpenVPN/openvpn/blob/v2.7.7/Changes.rst <https://github.com/OpenVPN/openvpn/blob/v2.7./Changes.rst>>

Source code and Windows installers can be downloaded from our download page:

<https://openvpn.net/community/>

Packages for Debian, Ubuntu, Fedora, RHEL, and openSUSE are available in the various
official Community repositories:

<https://community.openvpn.net/Pages/OpenVPN%20software%20repos>

Kind regards,
Yuriy Darnobyt

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