# CVE-2021-22890: curl: curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection d...

CVE-2021-22890 is fixed in 4 products on 1 platform, first by curl 7.68.0-1ubuntu2.5, released March 30, 2021. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-22890
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0306
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 30, 2021

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | curl Ubuntu 20.04 LTS (focal) | 7.68.0-1ubuntu2.5 | [curl 7.68.0-1ubuntu2.5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-curl-7.68.0-1ubuntu2.5.md) | Mar 30, 2021 |
| Linux | libcurl3-gnutls Ubuntu 20.04 LTS (focal) | 7.68.0-1ubuntu2.5 | [libcurl3-gnutls 7.68.0-1ubuntu2.5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libcurl3-gnutls-7.68.0-1ubuntu2.5.md) | Mar 30, 2021 |
| Linux | libcurl3-nss Ubuntu 20.04 LTS (focal) | 7.68.0-1ubuntu2.5 | [libcurl3-nss 7.68.0-1ubuntu2.5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libcurl3-nss-7.68.0-1ubuntu2.5.md) | Mar 30, 2021 |
| Linux | libcurl4 Ubuntu 20.04 LTS (focal) | 7.68.0-1ubuntu2.5 | [libcurl4 7.68.0-1ubuntu2.5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libcurl4-7.68.0-1ubuntu2.5.md) | Mar 30, 2021 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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