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Vulnerability record · CVE-2021-22890 · published 1 April 2021

CVE-2021-22890: Haxx libcurl authentication bypass by spoofing vulnerability

Haxx · Libcurl

curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3 session tickets. When using a HTTPS proxy and TLS 1.3, libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote server and then wrongly "short-cut" the host handshake. When confusing the tickets, a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed. Note that such a malicious HTTPS proxy needs to provide a certificate that curl will accept for the MITMed server for an attack to work - unless curl has been told to ignore the server certificate check.

3.7 CVSS 3.1 Low EPSS 3.1% · top 12.6% CWE-300 · CWE-300CWE-290 · Authentication bypass by spoofing
3.7CVSS 3.1 base score, v2 4.3
3.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
11Affected product versions listed by NVD
18References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3 session tickets. When using a HTTPS proxy and TLS 1.3, libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote server and then wrongly "short-cut" the host handshake. When confusing the tickets, a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed. Note that such a malicious HTTPS proxy needs to provide a certificate that curl will accept for the MITMed server for an attack to work - unless curl has been told to ignore the server certificate check.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

11 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://curl.se/docs/CVE-2021-22890.html PatchVendor Advisory
https://hackerone.com/reports/1129529 ExploitIssue TrackingPatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2ZC5BMIOKLBQJSFCHEDN2G2 Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ITVWPVGLFISU5BJC2BXBRYS Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KQUIOYX2KUU6FIUZVB5WWZ6 Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202105-36 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210521-0007/ Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://curl.se/docs/CVE-2021-22890.html PatchVendor Advisory
https://hackerone.com/reports/1129529 ExploitIssue TrackingPatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2ZC5BMIOKLBQJSFCHEDN2G2 Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ITVWPVGLFISU5BJC2BXBRYS Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KQUIOYX2KUU6FIUZVB5WWZ6 Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202105-36 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210521-0007/ Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-22890), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.