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Vulnerability record · CVE-2021-22926 · published 5 August 2021

CVE-2021-22926: Haxx curl improper certificate validation vulnerability

Haxx · Curl

libcurl-using applications can ask for a specific client certificate to be used in a transfer. This is done with the `CURLOPT_SSLCERT` option (`--cert` with the command line tool).When libcurl is built to use the macOS native TLS library Secure Transport, an application can ask for the client certificate by name or with a file name - using the same option. If the name exists as a file, it will be used instead of by name.If the appliction runs with a current working directory that is writable by other users (like `/tmp`), a malicious user can create a file name with the same name as the app wants to use by name, and thereby trick the application to use the file based cert instead of the one referred to by name making libcurl send the wrong client certificate in the TLS connection handshake.

7.5 CVSS 3.1 High EPSS 9.8% · top 4.6% CWE-840 · CWE-840CWE-295 · Improper certificate validation
7.5CVSS 3.1 base score, v2 5.0
9.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
19Affected product versions listed by NVD
22References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

libcurl-using applications can ask for a specific client certificate to be used in a transfer. This is done with the `CURLOPT_SSLCERT` option (`--cert` with the command line tool).When libcurl is built to use the macOS native TLS library Secure Transport, an application can ask for the client certificate by name or with a file name - using the same option. If the name exists as a file, it will be used instead of by name.If the appliction runs with a current working directory that is writable by other users (like `/tmp`), a malicious user can create a file name with the same name as the app wants to use by name, and thereby trick the application to use the file based cert instead of the one referred to by name making libcurl send the wrong client certificate in the TLS connection handshake.

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

Affected products

19 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://hackerone.com/reports/1234760 ExploitThird Party Advisory
https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org Mailing ListThird Party Advisory
https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.o Mailing ListThird Party Advisory
https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org Mailing ListThird Party Advisory
https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.o Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202212-01 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210902-0003/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20211022-0003/ Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://hackerone.com/reports/1234760 ExploitThird Party Advisory
https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org Mailing ListThird Party Advisory
https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.o Mailing ListThird Party Advisory
https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org Mailing ListThird Party Advisory
https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.o Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202212-01 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210902-0003/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20211022-0003/ Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-22926), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.