Patch Package:           OTP 27.3.4.9
Git Tag:                 OTP-27.3.4.9
Date:                    2026-03-12
Trouble Report Id:       OTP-19990, OTP-20007, OTP-20009, OTP-20011,
                         OTP-20022
Seq num:                 CVE-2026-23941, CVE-2026-23942,
                         CVE-2026-23943, ERIERL-1305, GH-10694,
                         GH-10698, PR-10707, PR-10723, PR-10811,
                         PR-10813, PR-10833
System:                  OTP
Release:                 27
Application:             inets-9.3.2.3, ssh-5.2.11.6, ssl-11.2.12.6
Predecessor:             OTP 27.3.4.8

Check out the git tag OTP-27.3.4.9, 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.

# inets-9.3.2.3

The inets-9.3.2.3 application can be applied independently of other applications
on a full OTP 27 installation.

## Fixed Bugs and Malfunctions

- The httpd server now rejects HTTP requests containing multiple Content-Length
  headers with different values, returning a 400 Bad Request response. This
  prevents potential HTTP request smuggling attacks. Thanks Luigino Camastra at
  Aisle Research for responsibly disclosing this vulnerability

  Own Id: OTP-20007
  Related Id(s): PR-10833, CVE-2026-23941

> #### Full runtime dependencies of inets-9.3.2.3
>
> erts-14.0, kernel-9.0, mnesia-4.12, public_key-1.13, runtime_tools-1.8.14,
> ssl-9.0, stdlib-5.0, stdlib-6.0

# ssh-5.2.11.6

The ssh-5.2.11.6 application can be applied independently of other applications
on a full OTP 27 installation.

## Fixed Bugs and Malfunctions

- Fixed path traversal vulnerability in SFTP server's root option allowing
  authenticated users to access sibling directories with matching name prefixes.
  The root option used string prefix matching instead of path component
  validation. With \{root, "/home/user1"\}, attackers could access /home/user10/
  or /home/user123/. Thanks to Luigino Camastra, Aisle Research.

  Own Id: OTP-20009
  Related Id(s): PR-10811, CVE-2026-23942

- Fixed excessive memory usage vulnerability in SSH compression allowing
  attackers to consume system resources through decompression bombs. The 'zlib'
  and 'zlib@openssh.com' algorithms lacked decompression size limits, allowing
  256 KB packets to expand to 255 MB (1029:1 ratio). This could lead to crashes
  on systems with limited memory.

  The fix removes zlib from default compression algorithms and implements
  decompression size limits for both algorithms. Thanks to Igor Morgenstern at
  Aisle Research

  Own Id: OTP-20011
  Related Id(s): PR-10813, CVE-2026-23943

> #### Full runtime dependencies of ssh-5.2.11.6
>
> 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-11.2.12.6

Note! The ssl-11.2.12.6 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-1.16.4 (first satisfied in OTP 27.1.3)

## Fixed Bugs and Malfunctions

- The NSS Keylogging refactoring mixed up of Read and Write connection states,
  could cause wrong NSS keylog labels, or `{error, closed}` returned without
  keylog.

  Own Id: OTP-19990
  Related Id(s): GH-10698, PR-10723

- TLS-1.3 certificate request now preserves the order of signature algorithms in
  certificate request extension to be in the servers preferred order, which
  might affect the choice made by some TLS clients.

  Own Id: OTP-20022
  Related Id(s): ERIERL-1305, GH-10694, PR-10707

> #### Full runtime dependencies of ssl-11.2.12.6
>
> crypto-5.0, erts-15.0, inets-5.10.7, kernel-9.0, public_key-1.16.4,
> runtime_tools-1.15.1, stdlib-6.0

# Thanks to

Hewwho