CyberRota Analysis
AI-GeneratedThe vulnerability affects NLnetLabs Unbound versions 1.20.0 through 1.26.0, specifically in the 'serve-expired' code path, allowing attackers to exploit the 'wait-limit' counter mechanism. By manipulating DNS queries with short TTLs, an attacker can maintain an unlimited number of pending queries from a single IP, effectively bypassing defenses against DNS amplification attacks. Organizations using these versions of Unbound should prioritize patching to mitigate potential abuse of this flaw.
Public Exploit Signal
A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.
Note: these links are listed for security research and verification purposes only.
Original NVD Description
In NLnetLabs Unbound 1.20.0 up to and including 1.26.0, a vulnerability on the 'serve-expired' code path can cause a double decrement on the 'wait-limit' counter per client IP essentially bypassing one of the counter measures that was introduced for DNSBomb (CVE-2024-33655). A malicious actor can exploit this by controlling an authoritative zone with short TTL, so cached entries expire quickly. Each 'slow' query, one the attacker's authoritative never answers, is followed by one query for an expired cached name, which is answered immediately via the 'serve-expired' path and decrements the counter twice. This second query was named 'pump'. By alternating slow queries and pumps, the attacker keeps the per-client counter at or below the configured 'wait-limit' indefinitely, and can hold an arbitrary number of pending queries from a single source IP, up to the global mesh quota (num-queries-per-thread); eventually bypassing one of the counter measures introduced for DNSBomb (CVE-2024-33655). This vulnerability is present on the 'serve-expired' code path.
Related CVEs
Other vulnerabilities affecting the same vendor(s)