Sec: Bump cowlib to 2.20.0 and gun to 2.6.0

Fixes:
  cowlib:
    EEF-CVE-2026-43971 (MEDIUM)
    aka: CVE-2026-43971
    Link Header Directive Smuggling via Unescaped target/rel/Attribute Keys in cow_link:link/1
    https://osv.dev/vulnerability/EEF-CVE-2026-43971

    EEF-CVE-2026-43966 (MEDIUM)
    aka: CVE-2026-43966, GHSA-w4f7-4cxr-rv3c
    HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2
    https://osv.dev/vulnerability/EEF-CVE-2026-43966

    EEF-CVE-2026-43969 (LOW)
    aka: CVE-2026-43969, GHSA-g2wm-735q-3f56
    Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1
    https://osv.dev/vulnerability/EEF-CVE-2026-43969
  gun:
    GHSA-w4f7-4cxr-rv3c (MEDIUM)
    aka: CVE-2026-43966, EEF-CVE-2026-43966
    cowboy and gun affected by an HTTP Request/Response Splitting vulnerability
    https://osv.dev/vulnerability/GHSA-w4f7-4cxr-rv3c

changelog.d/cowlib-2.20.0.security

@@ -0,0 +1 @@
+Update cowlib to version 2.20.0 which fixes HTTP splitting and header smuggling/injection vulnerabilities

changelog.d/gun-2.6.0.security

@@ -0,0 +1 @@
+Update gun to version 2.6.0 which fixes an HTTP request/response smuggling vulnerability

mix.exs

@@ -154,8 +154,8 @@ defmodule Pleroma.Mixfile do
       {:cachex, "~> 3.6"},
       {:tesla, "~> 1.20.0"},
       {:castore, "~> 1.0"},
-      {:cowlib, "~> 2.17.1"},
-      {:gun, "~> 2.4.1"},
+      {:cowlib, "~> 2.20"},
+      {:gun, "~> 2.6"},
       {:finch, "~> 0.20"},
       {:jason, "~> 1.4"},
       {:mogrify, "~> 0.9.3", override: true},

mix.lock

@@ -22,7 +22,7 @@
   "covertool": {:hex, :covertool, "2.0.7", "398be995c4cf1a2861174389b3577ca97beee43b60c8f1afcf510f1b07d32408", [:rebar3], [], "hexpm", "46158ed6e1a0df7c0a912e314c7b8e053bd74daa5fc6b790614922a155b5720c"},
   "cowboy": {:hex, :cowboy, "2.16.1", "fa04080b602ff25c40a7700f2dc0152dbc1ba26b42093ae0fa9bb7a337d5a242", [:make, :rebar3], [{:cowlib, ">= 2.16.0 and < 3.0.0", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, ">= 1.8.0 and < 3.0.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "b8ea4dd317a043e3177ec840cfa3bcb47cfb41035d3abb24d954dc7d51def399"},
   "cowboy_telemetry": {:hex, :cowboy_telemetry, "0.4.0", "f239f68b588efa7707abce16a84d0d2acf3a0f50571f8bb7f56a15865aae820c", [:rebar3], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "7d98bac1ee4565d31b62d59f8823dfd8356a169e7fcbb83831b8a5397404c9de"},
-  "cowlib": {:hex, :cowlib, "2.17.1", "3e6053016d1ab245730f0af688755476dcedb1c25ed8fb5751f59a2bfdc0c9af", [:make, :rebar3], [], "hexpm", "ff08bd17e6dd931445b18af77315b9b5fe052407110964ad2588c686b57b5e3f"},
+  "cowlib": {:hex, :cowlib, "2.20.0", "bb525377ba634cd6d68bac7bff5d98571f738806139d335daca827717c5dc172", [:make, :rebar3], [], "hexpm", "7d41a0dd2c093041ff3779ac5fe8a1585a68ec7cb2dd1de0536bdd2452fd7ba1"},
   "credo": {:hex, :credo, "1.7.12", "9e3c20463de4b5f3f23721527fcaf16722ec815e70ff6c60b86412c695d426c1", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "8493d45c656c5427d9c729235b99d498bd133421f3e0a683e5c1b561471291e5"},
   "crontab": {:hex, :crontab, "1.1.8", "2ce0e74777dfcadb28a1debbea707e58b879e6aa0ffbf9c9bb540887bce43617", [:mix], [{:ecto, "~> 1.0 or ~> 2.0 or ~> 3.0", [hex: :ecto, repo: "hexpm", optional: true]}], "hexpm"},
   "custom_base": {:hex, :custom_base, "0.2.1", "4a832a42ea0552299d81652aa0b1f775d462175293e99dfbe4d7dbaab785a706", [:mix], [], "hexpm", "8df019facc5ec9603e94f7270f1ac73ddf339f56ade76a721eaa57c1493ba463"},
@@ -57,7 +57,7 @@
   "floki": {:hex, :floki, "0.38.0", "62b642386fa3f2f90713f6e231da0fa3256e41ef1089f83b6ceac7a3fd3abf33", [:mix], [], "hexpm", "a5943ee91e93fb2d635b612caf5508e36d37548e84928463ef9dd986f0d1abd9"},
   "gen_smtp": {:hex, :gen_smtp, "0.15.0", "9f51960c17769b26833b50df0b96123605a8024738b62db747fece14eb2fbfcc", [:rebar3], [], "hexpm", "29bd14a88030980849c7ed2447b8db6d6c9278a28b11a44cafe41b791205440f"},
   "gettext": {:hex, :gettext, "0.24.0", "6f4d90ac5f3111673cbefc4ebee96fe5f37a114861ab8c7b7d5b30a1108ce6d8", [:mix], [{:expo, "~> 0.5.1", [hex: :expo, repo: "hexpm", optional: false]}], "hexpm", "bdf75cdfcbe9e4622dd18e034b227d77dd17f0f133853a1c73b97b3d6c770e8b"},
-  "gun": {:hex, :gun, "2.4.1", "c3a8bff8e155e1fc8e499216599bb7effbd27bc1985662a8b25016090dc18428", [:make, :rebar3], [{:cowlib, ">= 2.15.0 and < 3.0.0", [hex: :cowlib, repo: "hexpm", optional: false]}], "hexpm", "1450575b4d393aa0811322727b90ad1dd94b5c10026f54a1641785bcbd250384"},
+  "gun": {:hex, :gun, "2.6.0", "4672fe3d2e056d9314a4639db288b7e9ce0fe6be8f2f4dd4adba7d2b56f7927c", [:make, :rebar3], [{:cowlib, ">= 2.20.0 and < 3.0.0", [hex: :cowlib, repo: "hexpm", optional: false]}], "hexpm", "69bb957f4bd6c475b5714460fd65c26fc7eb85760aa64b74754de36ce5cced7d"},
   "h2": {:hex, :h2, "0.11.0", "b8c9f7c86f400582c5cbed59f79c0efd6cf49ad6478c210bede91d2d15019b14", [:rebar3], [], "hexpm", "c61f24361d0dc76375eaf35c2bf0e01235d81b7685538df571db036467fac358"},
   "hackney": {:hex, :hackney, "4.7.3", "42feec1a4986000411cb5d389bbc9fb61d9dff84c5eef42b11fc40ea327e6f9a", [:rebar3], [{:certifi, "~> 2.17.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:h2, "~> 0.11.0", [hex: :h2, repo: "hexpm", optional: false]}, {:idna, "~> 7.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:mimerl, "~> 1.5", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.4.2", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~> 1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:webtransport, "~> 0.4.4", [hex: :webtransport, repo: "hexpm", optional: false]}], "hexpm", "3f460e01d5a1abba39c32d06e9a733bb76e35d1ab87a83868b6bb29d646fe25f"},
   "hpax": {:hex, :hpax, "1.0.4", "777de5d433b0fbdc7c418159c8055910faa8047ffdb3d6b31098d2a46cd7685c", [:mix], [], "hexpm", "afc7cb142ebcc2d01ce7816190b98ce5dd49e799111b24249f3443d730f377ca"},