Description
Rack::Session is a session management implementation for Rack. From 2.0.0 to before 2.1.2, Rack::Session::Cookie incorrectly handles decryption failures when configured with secrets:. If cookie decryption fails, the implementation falls back to a default decoder instead of rejecting the cookie. This allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid session data without knowledge of any configured secret. Because this mechanism is used to load session state, an attacker can manipulate session contents and potentially gain unauthorized access. This vulnerability is fixed in 2.1.2.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| rack | rack-session | >= 2.0.0, < 2.1.2 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | ruby-rack-session | 2.1.1-0.2 | — |
| Debian 13 | ruby-rack-session | 2.1.1-0.1+deb13u1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | ruby-rack-session | 2.1.1-0.1ubuntu0.26.04.1 | — |
| Ubuntu 25.10 | ruby-rack-session | 2.1.1-0.1ubuntu0.1 | USN-8190-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | rubygem-rack-session | 2.1.2-1.1 | openSUSE-SU-2026:10604-1 |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | logstash-9.3 +2 | 9.3.3-r2 | — |
| Wolfi rolling | ruby3.2-rails-8.1 +1 | 8.1.3-r2 | — |
| Wolfi rolling | ruby3.3-rails-8.1 +1 | 8.1.3-r3 | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
GitHub 1 repository
-
sm1ee/CVE-2026-39324 ★ 0 · Apr 7, 2026
CVE-2026-39324: Rack Session auth bypass PoC
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| RubyGems | rack-session | >= 2.0.0, < 2.1.2 | 2.1.2 | GHSA-33qg-7wpp-89cq |
Advisories 2
- USN-8190-1 ruby-rack-session vulnerability Ubuntu Security Notices (USN) · Apr 27, 2026
- openSUSE-SU-2026:10604-1 ruby4.0-rubygem-rack-session-2.1.2-1.1 on GA media SUSE / openSUSE Security Updates · Apr 23, 2026