--- id: CVE-2021-22947 title: >- 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 summary: >- 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… severity: medium cvss: 5.9 cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N' cwe: - CWE-310 - CWE-345 vendor: haxx product: curl affected: - 'curl >= 7.20.0, < 7.79.0' - fedora = 33 - fedora = 35 - debian_linux = 9.0 - debian_linux = 10.0 - debian_linux = 11.0 - cloud_backup - clustered_data_ontap - h300s_firmware - h500s_firmware - h700s_firmware - h300e_firmware - h500e_firmware - h700e_firmware - h410s_firmware - solidfire_baseboard_management_controller_firmware - communications_cloud_native_core_binding_support_function = 1.11.0 - >- communications_cloud_native_core_network_function_cloud_native_environment = 1.10.0 - communications_cloud_native_core_network_repository_function = 1.15.0 - communications_cloud_native_core_network_repository_function = 1.15.1 - communications_cloud_native_core_network_slice_selection_function = 1.8.0 - communications_cloud_native_core_service_communication_proxy = 1.15.0 - 'mysql_server >= 5.7.0, <= 5.7.35' - 'mysql_server >= 8.0.0, <= 8.0.26' - peoplesoft_enterprise_peopletools = 8.57 - peoplesoft_enterprise_peopletools = 8.58 - peoplesoft_enterprise_peopletools = 8.59 - sinec_infrastructure_network_services < 1.0.1.1 - macos < 12.3 - commerce_guided_search = 11.3.2 - communications_cloud_native_core_binding_support_function = 22.1.3 - communications_cloud_native_core_console = 22.2.0 - communications_cloud_native_core_network_repository_function = 22.1.2 - communications_cloud_native_core_network_repository_function = 22.2.0 - communications_cloud_native_core_security_edge_protection_proxy = 22.1.1 - 'universal_forwarder >= 8.2.0, < 8.2.12' - 'universal_forwarder >= 9.0.0, < 9.0.6' - universal_forwarder = 9.1.0 patched: - curl 7.79.0 - sinec_infrastructure_network_services 1.0.1.1 - macos 12.3 - universal_forwarder 9.0.6 published: '2021-09-29' updated: '2026-10-14' sourceUpdated: '2026-10-14T12:17:09.210' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-22947' references: - url: 'http://seclists.org/fulldisclosure/2022/Mar/29' label: support@hackerone.com - url: 'https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf' label: support@hackerone.com - url: 'https://hackerone.com/reports/1334763' label: support@hackerone.com - url: 'https://lists.debian.org/debian-lts-announce/2021/09/msg00022.html' label: support@hackerone.com - url: 'https://lists.debian.org/debian-lts-announce/2022/08/msg00017.html' label: support@hackerone.com - url: >- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOAK4X73EJTAPTSVT7IRVDMUWVXNWGD/ label: support@hackerone.com - url: >- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLEC6YVEM2HWUBX67SDGPSY4CQB72OE/ label: support@hackerone.com - url: 'https://security.gentoo.org/glsa/202212-01' label: support@hackerone.com - url: 'https://security.netapp.com/advisory/ntap-20211029-0003/' label: support@hackerone.com - url: 'https://support.apple.com/kb/HT213183' label: support@hackerone.com - url: 'https://www.debian.org/security/2022/dsa-5197' label: support@hackerone.com - url: 'https://www.oracle.com/security-alerts/cpuapr2022.html' label: support@hackerone.com - url: 'https://www.oracle.com/security-alerts/cpujan2022.html' label: support@hackerone.com - url: 'https://www.oracle.com/security-alerts/cpujul2022.html' label: support@hackerone.com - url: 'https://www.oracle.com/security-alerts/cpuoct2021.html' label: support@hackerone.com - url: 'http://seclists.org/fulldisclosure/2022/Mar/29' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://hackerone.com/reports/1334763' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://lists.debian.org/debian-lts-announce/2021/09/msg00022.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://lists.debian.org/debian-lts-announce/2022/08/msg00017.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: >- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOAK4X73EJTAPTSVT7IRVDMUWVXNWGD/ label: af854a3a-2127-422b-91ae-364da2661108 - url: >- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLEC6YVEM2HWUBX67SDGPSY4CQB72OE/ label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://security.gentoo.org/glsa/202212-01' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://security.netapp.com/advisory/ntap-20211029-0003/' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://support.apple.com/kb/HT213183' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.debian.org/security/2022/dsa-5197' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.oracle.com/security-alerts/cpuapr2022.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.oracle.com/security-alerts/cpujan2022.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.oracle.com/security-alerts/cpujul2022.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.oracle.com/security-alerts/cpuoct2021.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://cert-portal.siemens.com/productcert/html/ssa-389290.html' label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e - url: 'https://cert-portal.siemens.com/productcert/html/ssa-398330.html' label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e tags: - nvd epss: 0.03009 epssPercentile: 0.87075 ingestedAt: '2026-10-14T12:29:10.827Z' --- ## Overview 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. ## Affected - `curl >= 7.20.0, < 7.79.0` - `fedora = 33` - `fedora = 35` - `debian_linux = 9.0` - `debian_linux = 10.0` - `debian_linux = 11.0` - `cloud_backup` - `clustered_data_ontap` - `h300s_firmware` - `h500s_firmware` - `h700s_firmware` - `h300e_firmware` - `h500e_firmware` - `h700e_firmware` - `h410s_firmware` - `solidfire_baseboard_management_controller_firmware` - `communications_cloud_native_core_binding_support_function = 1.11.0` - `communications_cloud_native_core_network_function_cloud_native_environment = 1.10.0` - `communications_cloud_native_core_network_repository_function = 1.15.0` - `communications_cloud_native_core_network_repository_function = 1.15.1` - `communications_cloud_native_core_network_slice_selection_function = 1.8.0` - `communications_cloud_native_core_service_communication_proxy = 1.15.0` - `mysql_server >= 5.7.0, <= 5.7.35` - `mysql_server >= 8.0.0, <= 8.0.26` - `peoplesoft_enterprise_peopletools = 8.57` - `peoplesoft_enterprise_peopletools = 8.58` - `peoplesoft_enterprise_peopletools = 8.59` - `sinec_infrastructure_network_services < 1.0.1.1` - `macos < 12.3` - `commerce_guided_search = 11.3.2` - `communications_cloud_native_core_binding_support_function = 22.1.3` - `communications_cloud_native_core_console = 22.2.0` - `communications_cloud_native_core_network_repository_function = 22.1.2` - `communications_cloud_native_core_network_repository_function = 22.2.0` - `communications_cloud_native_core_security_edge_protection_proxy = 22.1.1` - `universal_forwarder >= 8.2.0, < 8.2.12` - `universal_forwarder >= 9.0.0, < 9.0.6` - `universal_forwarder = 9.1.0` ## Remediation Upgrade past the affected range: - `curl 7.79.0` - `sinec_infrastructure_network_services 1.0.1.1` - `macos 12.3` - `universal_forwarder 9.0.6`