SB2022121904 - Gentoo update for Unbound
Published: December 19, 2022
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 3 secuirty vulnerabilities.
1) Predictable from Observable State (CVE-ID: CVE-2022-30698)
The vulnerability allows a remote attacker to poison DNS cache.
The vulnerability exists due to the way Unbound handles delegation information expiration event. A remote attacker who controls a rouge DNS server can force the Unbound instance to cache incorrect information about subdomain delegation and permanently poison the DNS cache, e.g. perform the "ghost domain names" attack.
The attack is carried out when Unbound is queried for a subdomain of a rogue domain name. The rogue nameserver returns delegation information for the subdomain that updates Unbound's delegation cache. This action can be repeated before expiry of the delegation information by querying Unbound for a second level subdomain which the rogue nameserver provides new delegation information. Since Unbound is a child-centric resolver, the ever-updating child delegation information can keep a rogue domain name resolvable long after revocation.2) Predictable from Observable State (CVE-ID: CVE-2022-30699)
The vulnerability allows a remote attacker to poison DNS cache.
The vulnerability exists due to the way Unbound handles delegation information expiration event. A remote attacker who controls a rouge DNS server can force the Unbound instance to cache incorrect information about domain delegation and permanently poison the DNS cache, e.g. perform the "ghost domain names" attack.
The attack is perform when Unbound is queried for a rogue domain name, which cached delegation information is about to expire. The rogue nameserver delays the response until the cached delegation information expires. Upon receiving the delayed answer containing the delegation information, Unbound overwrites the now expired entries.
3) Resource exhaustion (CVE-ID: CVE-2022-3204)
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 when processing a malicious delegation with a considerable number of non responsive nameservers. A remote attacker can trigger CPU high usage and perform a denial of service (DoS) attack.
The attack is known as "Non-Responsive Delegation Attack" (NRDelegation Attack).
Remediation
Install update from vendor's website.