Detections
Analytics

Ubuntu 26.04 LTS : Rack vulnerabilities (USN-8989-1)

high Nessus Plugin ID 375782

Synopsis

The remote Ubuntu host is missing one or more security updates.

Description

The remote Ubuntu 26.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-8989-1 advisory.

 Andrew Lacambra discovered that Rack did not properly parse certain regular expressions. An attacker could possibly use this issue to bypass network security filters. (CVE-2026-26961)

 William T. Nelson discovered that Rack did not handle multipart headers correctly. An attacker could possibly use this issue to cause downstream parsing issues or a denial of service. (CVE-2026-26962)

 It was discovered that Rack did not handle the Forwarded header correctly. An attacker could possibly use this issue to manipulate header values. (CVE-2026-32762)

 It was discovered that Rack could consume excessive CPU when handling certain Accept-Encoding values. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-34230)

 Haruki Oyama discovered that certain configurations of Rack could erroneously fail to derive the displayed directory path, and expose the full file system path. An attacker could possibly use this issue to disclose deployment details such as layout and usernames. (CVE-2026-34763)

 It was discovered that Rack did not properly handle static file paths. An attacker could possibly use this issue to exfiltrate unintentionally served data. (CVE-2026-34785)

 Haruki Oyama discovered that Rack did not apply header rules to certain requests for URL-encoded static paths. An attacker could possibly use this issue to bypass security-relevant response headers.
 (CVE-2026-34786)

 It was discovered that Rack did not limit the number of ranges requested in the Range header. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-34826)

 It was discovered that Rack could consume excessive CPU when parsing certain multipart parameters. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-34827)

 It was discovered that Rack could consume unbounded disk space when handling requests without a Content- Length header. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-34829)

 Mehtab Zafar discovered that Rack directly interpreted the X-Accel-Mapping header as a regular expression without escaping. An attacker could possibly use this issue to exfiltrate arbitrary files from internal locations. (CVE-2026-34830)

 It was discovered that Rack did not properly handle messages with Unicode. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-34831)

 It was discovered that Rack did not properly parse the Host header. An attacker could possibly use this issue to bypass security filters or poison generated links. (CVE-2026-34835)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected ruby-rack package.

See Also

https://ubuntu.com/security/notices/USN-8989-1

Plugin Details

Severity: High

ID: 375782

File Name: ubuntu_USN-8989-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 11/4/2026

Updated: 11/4/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Continuous Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.73

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.1

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:N/A:N

CVSS Score Source: CVE-2026-34830

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.7

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:26.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:ruby-rack

Required KB Items: Host/cpu, Host/Debian/dpkg-l, Host/Ubuntu, Host/Ubuntu/release

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 11/3/2026

Vulnerability Publication Date: 4/2/2026

Reference Information

CVE: CVE-2026-26961, CVE-2026-26962, CVE-2026-32762, CVE-2026-34230, CVE-2026-34763, CVE-2026-34785, CVE-2026-34786, CVE-2026-34826, CVE-2026-34827, CVE-2026-34829, CVE-2026-34830, CVE-2026-34831, CVE-2026-34835

USN: 8989-1