SB2026103127 - Ubuntu update for c-ares
Published: October 31, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 4 vulnerabilities.
1) Out-of-bounds read (CVE-ID: CVE-2020-22217)
CWE-ID: CWE-125 - Out-of-bounds read
CVSSv4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a boundary condition within the ares_parse_soa_reply() function in ares_parse_soa_reply.c. A remote attacker can trigger an out-of-bounds read error and crash the application.
2) Buffer overflow (CVE-ID: CVE-2022-4904)
CWE-ID: CWE-119 - Memory corruption
CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
The vulnerability allows a local user to perform a denial of service (DoS) attack.
The vulnerability exists due to a boundary error within the config_sortlist() function. A local user can trigger memory corruption and perform a denial of service (DoS) attack.
3) Inefficient Algorithmic Complexity (CVE-ID: CVE-2026-69184)
CWE-ID: CWE-407 - Inefficient Algorithmic Complexity
CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to inefficient algorithmic complexity in ares_dns_name_parse() when parsing crafted DNS responses with unbounded compression pointer chains. A remote attacker can send a specially crafted DNS response to cause a denial of service.
Because c-ares runs on a single-threaded event loop, parsing a crafted response can stall all resolution for the duration.
4) Resource exhaustion (CVE-ID: CVE-2026-69186)
CWE-ID: CWE-400 - Resource exhaustion
CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in the DNS response parser when parsing DNS responses. A remote attacker can send a specially crafted DNS response with forged header record counts to cause a denial of service.
The issue is triggered before transaction-ID validation or question matching, and sustained exploitation is required to produce allocator pressure that degrades availability.
Remediation
Install update from vendor's website.