CVE-2021-22924Public exploitNetwork attack vector

Certificate verification bypass via flawed connection reuse

Published Aug 5, 2021 · Updated Jun 9, 2025

Improper certificate validation in curl 7.10.4 through 7.77.0 allows remote attackers to receive data over a wrongly reused TLS connection. Curl_ssl_config_matches omits the issuer certificate and compares certificate-path fields without case sensitivity, treating distinct SSL configurations as equal. Exploitation requires reusable transfers to the same destination with different issuer certificates or case-colliding paths, and the reported impact is limited to confidentiality.

CVSS severity7.4
High
EPSS probability6.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in curl 7.10.4 through 7.77.0 allows remote attackers to receive data over a wrongly reused TLS connection. Curl_ssl_config_matches omits the issuer certificate and compares certificate-path fields without case sensitivity, treating distinct SSL configurations as equal. Exploitation requires reusable transfers to the same destination with different issuer certificates or case-colliding paths, and the reported impact is limited to confidentiality.

The record

CVE
CVE-2021-22924
Published
Aug 5, 2021
Updated
Jun 9, 2025
Vendor
curl
Product
curl
Classifications
CWE-20, CWE-295, CWE-706
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=curl 7.10.4 to and include curl 7.77.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=curl 7.10.4 to and include curl 7.77.0

Published CVSS scores

3.7CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
5.8NISTAV:N/AC:M/Au:N/C:P/I:P/A:N
7.4NISTCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-295Improper Certificate Validation
CWE-706Use of Incorrectly-Resolved Name or Reference

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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