SB2026041762 - Ubuntu update for ruby-rack
Published: April 17, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 13 secuirty vulnerabilities.
1) Interpretation Conflict (CVE-ID: CVE-2026-26961)
The vulnerability allows a remote attacker to compromise the target system.
The vulnerability exists due to the "Rack::Multipart::Parser" extracts the "boundary" parameter from multipart/form-data using a greedy regular expression. A remote attacker can bypass upstream filtering of uploaded files or form fields.
2) CRLF injection (CVE-ID: CVE-2026-26962)
The vulnerability allows a remote attacker to inject arbitrary data in server response.
The vulnerability exists due to insufficient validation of attacker-supplied data within Rack::Multipart::Parser. A remote attacker can pass specially crafted data to the application containing CR-LF characters and modify application behavior.
3) Interpretation Conflict (CVE-ID: CVE-2026-32762)
The vulnerability allows a remote attacker to compromise the target system.
The vulnerability exists due to interpretation conflict in the "Forwarded" header. A remote attacker can gain access to values for "host", "proto", "for" or related URL components
4) Resource exhaustion (CVE-ID: CVE-2026-34230)
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources in "Rack::Utils.select_best_encoding". A remote attacker can trigger resource exhaustion and perform a denial of service (DoS) attack.
5) Permissive Regular Expression (CVE-ID: CVE-2026-34763)
The vulnerability allows a remote attacker to gain access to sensitive information on the system.
The vulnerability exists due to unescaped regex interpolation in "Rack::Directory". A remote attacker can cause Root directory disclosure on the system.
6) Partial String Comparison (CVE-ID: CVE-2026-34785)
The vulnerability allows a remote attacker to gain access to potentially sensitive information.
The vulnerability exists due to partial string comparison issue in "Rack::Static". A remote attacker can gain unauthorized access to sensitive information on the system.
7) Incorrect Behavior Order: Validate Before Canonicalize (CVE-ID: CVE-2026-34786)
The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.
The vulnerability exists due to incorrect behavior order when "Rack::Static#applicable_rules" evaluates several "header_rules" types. A remote attacker can request an encoded form of the path and bypass those headers.
8) Resource exhaustion (CVE-ID: CVE-2026-34826)
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources within excessive overlapping ranges. A remote attacker can trigger resource exhaustion and perform a denial of service (DoS) attack.
9) Resource exhaustion (CVE-ID: CVE-2026-34827)
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources within escape-heavy quoted parameters.. A remote attacker can trigger resource exhaustion and perform a denial of service (DoS) attack.
10) Resource exhaustion (CVE-ID: CVE-2026-34829)
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to application does not properly control consumption of internal resources without "Content-Length" header. A remote attacker can trigger resource exhaustion and perform a denial of service (DoS) attack.
11) Permissive Regular Expression (CVE-ID: CVE-2026-34830)
The vulnerability allows a remote attacker to gain access to sensitive information on the system.
The vulnerability exists due to permissive regular expression in "Rack::Sendfile#map_accel_path". A remote attacker can cause nginx to serve unintended files from configured internal locations.
12) Improper Handling of Length Parameter Inconsistency (CVE-ID: CVE-2026-34831)
The vulnerability allows a remote attacker to compromise the target system.
The vulnerability exists due to "Content-Length" mismatch in "Rack::Files" error responses. A remote attacker can cause response parsing inconsistencies or response desynchronization.
13) Improper Validation of Syntactic Correctness of Input (CVE-ID: CVE-2026-34835)
The vulnerability allows a remote attacker to compromise the target system.
The vulnerability exists due to the "Rack::Request" accepts invalid Host characters. A remote attacker can bypass host allowlists and poison generated links, redirects, or origin-dependent security decisions.
Remediation
Install update from vendor's website.