{"cve":{"cve_id":"CVE-2025-5994","is_kev":false,"kev_date_added":null,"kev_vendor_project":null,"kev_product":null,"kev_vulnerability_name":null,"kev_short_description":null,"kev_required_action":null,"kev_due_date":null,"kev_known_ransomware":null,"kev_notes":null,"kev_cwes":null,"epss_score":0.0019,"epss_percentile":0.0868,"epss_as_of":"2026-06-23","description":"A multi-vendor cache poisoning vulnerability named 'Rebirthday Attack' has been discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is also vulnerable when compiled with ECS support, i.e., '--enable-subnet', AND configured to send ECS information along with queries to upstream name servers, i.e., at least one of the 'send-client-subnet', 'client-subnet-zone' or 'client-subnet-always-forward' options is used. Resolvers supporting ECS need to segregate outgoing queries to accommodate for different outgoing ECS information. This re-opens up resolvers to a birthday paradox attack (Rebirthday Attack) that tries to match the DNS transaction ID in order to cache non-ECS poisonous replies.","published_at":"2025-07-16T14:38:22.738000Z","last_modified_at":null,"cvss_v3_score":null,"cvss_v3_vector":null,"cvss_v3_severity":null,"cvss_v4_score":8.7,"cvss_v4_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/R:U/V:C","cvss_v4_severity":"HIGH","ssvc_decision":null,"ssvc_exploitation":null,"ssvc_automatable":null,"ssvc_technical_impact":null,"cwes":["CWE-349"],"nvd_references":["https://nlnetlabs.nl/downloads/unbound/CVE-2025-5994.txt"],"vuln_status":null,"trending_score":null,"is_trending":false,"has_trended":false,"trended_number_one":false,"trending_peak_score":null,"trending_peak_rank":null,"started_trending_at":null,"trended_number_one_at":null,"summary_generated":null,"summary_generated_at":null,"summary_model":null,"created_at":"2026-06-24T00:09:39.878444Z","updated_at":"2026-06-28T23:27:52.812686Z"},"effective_severity":"HIGH","badges":[],"impact_analysis":[],"cvss_v3_decoded":{"version":null,"metrics":[]},"cvss_v4_decoded":{"version":"4.0","metrics":[{"metric":"AV","name":"Attack Vector","value":"N","value_label":"Network"},{"metric":"AC","name":"Attack Complexity","value":"L","value_label":"Low"},{"metric":"AT","name":"Attack Requirements","value":"N","value_label":"None"},{"metric":"PR","name":"Privileges Required","value":"N","value_label":"None"},{"metric":"UI","name":"User Interaction","value":"N","value_label":"None"},{"metric":"VC","name":"Confidentiality (Vulnerable System)","value":"N","value_label":"None"},{"metric":"VI","name":"Integrity (Vulnerable System)","value":"H","value_label":"High"},{"metric":"VA","name":"Availability (Vulnerable System)","value":"N","value_label":"None"},{"metric":"SC","name":"Confidentiality (Subsequent System)","value":"N","value_label":"None"},{"metric":"SI","name":"Integrity (Subsequent System)","value":"N","value_label":"None"},{"metric":"SA","name":"Availability (Subsequent System)","value":"N","value_label":"None"},{"metric":"R","name":"R","value":"U","value_label":"Unchanged"},{"metric":"V","name":"V","value":"C","value_label":"Changed"}]},"affected":[{"vendor_slug":"nlnet-labs","vendor_name":"NLnet Labs","product_slug":"unbound","product_name":"Unbound","version_start":"1.6.2","version_start_inclusive":true,"version_end":"1.23.0","version_end_inclusive":false,"cpe23_uri":"cve5:nlnet-labs:unbound:1.6.2:1.23.0"}],"exploit_refs":[],"news":[],"references":[{"url":"https://nlnetlabs.nl/downloads/unbound/CVE-2025-5994.txt","source_type":"MISC","tags":[]}],"timeline":[{"type":"published","at":"2025-07-16T14:38:22.738000Z","label":"CVE published","source":null},{"type":"cvss_changed","at":"2026-06-28T17:48:34.338798Z","label":"CVSS score revised","source":"cvelistv5"},{"type":"cvss_changed","at":"2026-06-28T17:48:34.338798Z","label":"CVSS score revised","source":"cvelistv5"},{"type":"cvss_changed","at":"2026-06-28T17:48:34.338798Z","label":"CVSS score revised","source":"cvelistv5"}]}