Vulnerability Report

CVE-2021-22947

Title: curl MITM via cached responses after STARTTLS

Other

Proof Of Concept

No public PoC currently indexed for CVE-2021-22947.

CWE Category CWE-345
Published Date Sep 29, 2021
Modified Date Apr 16, 2026
Exploit Status Not Found
Score 5.9 CVSS v3.1
Exploit Probability (EPSS)
2.80%

Vulnerability Summary

CVE-2021-22947: 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.

Impacted Vendors

Reference Links

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 https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOAK4X73EJTAPTSVT7IRVDMUWVXNWGD/ https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLEC6YVEM2HWUBX67SDGPSY4CQB72OE/ https://security.gentoo.org/glsa/202212-01 https://security.netapp.com/advisory/ntap-20211029-0003/ https://support.apple.com/kb/HT213183 https://www.debian.org/security/2022/dsa-5197 https://www.oracle.com/security-alerts/cpuapr2022.html https://www.oracle.com/security-alerts/cpujan2022.html https://www.oracle.com/security-alerts/cpujul2022.html https://www.oracle.com/security-alerts/cpuoct2021.html 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 https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/APOAK4X73EJTAPTSVT7IRVDMUWVXNWGD/ https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RWLEC6YVEM2HWUBX67SDGPSY4CQB72OE/ https://security.gentoo.org/glsa/202212-01 https://security.netapp.com/advisory/ntap-20211029-0003/ https://support.apple.com/kb/HT213183 https://www.debian.org/security/2022/dsa-5197 https://www.oracle.com/security-alerts/cpuapr2022.html https://www.oracle.com/security-alerts/cpujan2022.html https://www.oracle.com/security-alerts/cpujul2022.html https://www.oracle.com/security-alerts/cpuoct2021.html
CVSS v3.1
Source Entity [email protected]
Severity MEDIUM
5.9
Attack Vector
NETWORK
Complexity
HIGH
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v3.1
Source Entity 134c704f-9b21-4f2e-91b3-4a467353bcc0
Severity MEDIUM
5.9
Attack Vector
NETWORK
Complexity
HIGH
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v2.0
Source Entity [email protected]
Severity MEDIUM
4.3
Access Vector
N/A
Authentication
N/A
RAW VECTOR AV:N/AC:M/Au:N/C:N/I:P/A:N

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2021-22947 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

MODIFIED

Vulnerability data updated via NVD.

MODIFIED

Vulnerability data or affected products updated.

PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector NETWORK
Complexity HIGH
Privileges N/A
Interaction NONE
CVSS Vector String CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected Stack

No specific products linked.