Patch Package: OTP 27.3.4.18 Git Tag: OTP-27.3.4.18 Date: 2026-09-22 Trouble Report Id: OTP-20256, OTP-20272, OTP-20287, OTP-20327, OTP-20355, OTP-20358, OTP-20365, OTP-20367, OTP-20371, OTP-20384, OTP-20386, OTP-20388, OTP-20390 Seq num: CVE-2026-65634, CVE-2026-68956, CVE-2026-89422, ERIERL-1355, ERIERL-1356, ERIERL-1363, GH-11338, GH-11344, GH-11534, GH-11586, GH-11619, GH-SA-qhcm-px9c-rvfh, PR-11356, PR-11426, PR-11523, PR-11559, PR-11566, PR-11570, PR-11574, PR-11616, PR-11632, PR-11638, PR-11641, PR-11651, PR-11655 System: OTP Release: 27 Application: asn1-5.3.4.3, compiler-8.6.1.7, mnesia-4.23.5.5, public_key-1.17.1.6, ssh-5.2.11.13, ssl-11.2.12.13 Predecessor: OTP 27.3.4.17 Check out the git tag OTP-27.3.4.18, and build a full OTP system including documentation. Apply one or more applications from this build as patches to your installation using the 'otp_patch_apply' tool. For information on install requirements, see descriptions for each application version below. # POTENTIAL INCOMPATIBILITIES - Fixed a vulnerability where the `max_channels` daemon option was not enforced for session channels without an active subsystem, allowing a remote authenticated user to open an infinite number of channels and exhaust server resources despite the configured limit. The default value of the max_channels daemon option has been changed from infinity to 256. Deployments requiring more than 256 simultaneous channels per connection can restore the previous behavior by setting `{max_channels, infinity}`. The default value of the max_sessions daemon option has been changed from infinity to 1024. Deployments requiring more concurrent SSH connections can restore the previous behavior by setting `{max_sessions, infinity}`. Own Id: OTP-20287 Application(s): ssh Related Id(s): GH-SA-qhcm-px9c-rvfh, PR-11523, CVE-2026-68956 # asn1-5.3.4.3 The asn1-5.3.4.3 application can be applied independently of other applications on a full OTP 27 installation. ## Fixed Bugs and Malfunctions - Fixed a denial-of-service attack in asn1, where abnormally large OID components (arcs) could cause resource exhaustion. Own Id: OTP-20272 Related Id(s): PR-11655, CVE-2026-65634 - The JER backend will no longer break certain values (true, false, null) when they are typed as ENUMERATED, they will now be encoded as strings as required by the standard. Own Id: OTP-20355 Related Id(s): ERIERL-1355, PR-11559 > #### Full runtime dependencies of asn1-5.3.4.3 > > erts-14.0, kernel-9.0, stdlib-5.0 # compiler-8.6.1.7 The compiler-8.6.1.7 application can be applied independently of other applications on a full OTP 27 installation. ## Fixed Bugs and Malfunctions - In rare circumstances, the type analysis pass of the compiler could run for many minutes. Own Id: OTP-20365 Related Id(s): GH-11534, PR-11566 - Certain uses of funs could crash the compiler. For example: f() -> F = fun Fn(0) -> 0; Fn(N) -> Fn(N - 1) end, [F(X) || X <- [1, 2]]. This has been corrected. Own Id: OTP-20386 Related Id(s): GH-11619, PR-11638 > #### Full runtime dependencies of compiler-8.6.1.7 > > crypto-5.1, erts-13.0, kernel-8.4, stdlib-6.0 # mnesia-4.23.5.5 The mnesia-4.23.5.5 application can be applied independently of other applications on a full OTP 27 installation. ## Fixed Bugs and Malfunctions - Fixed mnesia:force_load_table/1 getting stuck when the remote node becomes unreachable during table loading. When a network loader is aborted due to sender node going down and a user has forced a table load, we now retry loading from disc instead. Additionally, for disc_only_copies tables, the process actually loading the table is the dets server process, not the mnesia loader, so it would not receive the abort notification and would hang indefinitely. Now it correctly receives the notification and aborts table loading. Own Id: OTP-20256 Related Id(s): GH-11344, PR-11426 > #### Full runtime dependencies of mnesia-4.23.5.5 > > erts-9.0, kernel-5.3, stdlib-5.0 # public_key-1.17.1.6 The public_key-1.17.1.6 application can be applied independently of other applications on a full OTP 27 installation. ## Fixed Bugs and Malfunctions - Align moduli and pubkey_moduli.hrl to state on OTP-28 and newer. Own Id: OTP-20367 Related Id(s): PR-11574 > #### Full runtime dependencies of public_key-1.17.1.6 > > asn1-5.0, crypto-5.0, erts-13.0, kernel-8.0, stdlib-4.0 # ssh-5.2.11.13 The ssh-5.2.11.13 application can be applied independently of other applications on a full OTP 27 installation. ## Fixed Bugs and Malfunctions - Fixed a vulnerability where the `max_channels` daemon option was not enforced for session channels without an active subsystem, allowing a remote authenticated user to open an infinite number of channels and exhaust server resources despite the configured limit. The default value of the max_channels daemon option has been changed from infinity to 256. Deployments requiring more than 256 simultaneous channels per connection can restore the previous behavior by setting `{max_channels, infinity}`. The default value of the max_sessions daemon option has been changed from infinity to 1024. Deployments requiring more concurrent SSH connections can restore the previous behavior by setting `{max_sessions, infinity}`. Own Id: OTP-20287 Related Id(s): GH-SA-qhcm-px9c-rvfh, PR-11523, CVE-2026-68956 *** POTENTIAL INCOMPATIBILITY *** - The SSH daemon no longer rejects a `subsystem` request that is preceded by `env` or `pty-req` request on the same channel. Own Id: OTP-20371 Related Id(s): ERIERL-1363, GH-11586, PR-11616 > #### Full runtime dependencies of ssh-5.2.11.13 > > crypto-5.0, erts-14.0, kernel-9.0, public_key-1.6.1, runtime_tools-1.15.1, > stdlib-5.0, stdlib-6.0 # ssl-11.2.12.13 Note! The ssl-11.2.12.13 application _cannot_ be applied independently of other applications on an arbitrary OTP 27 installation. On a full OTP 27 installation, also the following runtime dependency has to be satisfied: -- public_key-1.17.1.3 (first satisfied in OTP 27.3.4.12) ## Fixed Bugs and Malfunctions - Undecodable `certificate_authorities` names are now skipped, as they are just a hint. Own Id: OTP-20327 Related Id(s): GH-11338, PR-11356 - Corrected generated keylog information generated from the `keylog_hs` option in the corner case that it was invoked after the client had reached its connection state, but the server closed the connection before it reached its connection state. Own Id: OTP-20358 Related Id(s): ERIERL-1356, PR-11570 - Fix restart bug for TLS-1.3 session ticket server, introduced by backport commit in OTP-27.3.4.14, would case a restart to fail due to wrong number of arguments. Own Id: OTP-20384 Related Id(s): PR-11632 - Reject unsolicited TLS-1.3 pre_shared_key in client. Own Id: OTP-20388 Related Id(s): PR-11641, CVE-2026-89422 - Security and robustness hardening returning RFC mandated alert reasons, narrowing/correcting length checks. Correct signature algorithm handling that slightly mixed up signature algorithms and signature algorithms cert in TLS-1.2. Add missing TLS-1.3 Brainpool groups support. (Not relevant in 27 patch) Enhanced/corrected documentation and spec errors/deviations. Own Id: OTP-20390 Related Id(s): PR-11651 > #### Full runtime dependencies of ssl-11.2.12.13 > > crypto-5.1, erts-15.0, inets-5.10.7, kernel-9.0, public_key-1.17.1.3, > runtime_tools-1.15.1, stdlib-6.0 # Thanks to Alex Nogueira, ausimian