{"cve":"CVE-2021-22947","nvd":{"published":"2021-09-29T20:15:08.253","modified":"2026-10-14T12:17:09.210","status":"Modified","description":"When curl >= 7.20.0 and <= 7.78.0 connects to an IMAP or POP3 server to retrieve data using STARTTLS to upgrade to TLS security, the server can respond and send back multiple responses at once that curl caches. curl would then upgrade to TLS but not flush the in-queue of cached responses but instead continue using and trustingthe responses it got *before* the TLS handshake as if they were authenticated.Using this flaw, it allows a Man-In-The-Middle attacker to first inject the fake responses, then pass-through the TLS traffic from the legitimate server and trick curl into sending data back to the user thinking the attacker's injected data comes from the TLS-protected server.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","score":5.9},"cwes":["CWE-345","CWE-310"],"references":["http://seclists.org/fulldisclosure/2022/Mar/29","https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf","https://hackerone.com/reports/1334763","https://lists.debian.org/debian-lts-announce/2021/09/msg00022.html","https://lists.debian.org/debian-lts-announce/2022/08/msg00017.html"],"products":["apple:macos","debian:debian_linux","fedoraproject:fedora","haxx:curl","netapp:cloud_backup","netapp:clustered_data_ontap","netapp:h300e_firmware","netapp:h300s_firmware","netapp:h410s_firmware","netapp:h500e_firmware","netapp:h500s_firmware","netapp:h700e_firmware","netapp:h700s_firmware","netapp:solidfire_baseboard_management_controller_firmware","oracle:commerce_guided_search","oracle:communications_cloud_native_core_binding_support_function","oracle:communications_cloud_native_core_console","oracle:communications_cloud_native_core_network_function_cloud_native_environment","oracle:communications_cloud_native_core_network_repository_function","oracle:communications_cloud_native_core_network_slice_selection_function","oracle:communications_cloud_native_core_security_edge_protection_proxy","oracle:communications_cloud_native_core_service_communication_proxy","oracle:mysql_server","oracle:peoplesoft_enterprise_peopletools","siemens:sinec_infrastructure_network_services","splunk:universal_forwarder"],"source":"nvd","synced_at":"2026-10-19T21:23:41.316049955+00:00"},"epss":{"cve":"CVE-2021-22947","score":0.03009,"percentile":0.87304,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}