# CVE-2021-22890: Security feature bypass in https://github.com/curl/curl

> A malicious HTTPS proxy can bypass TLS certificate checks in libcurl via session ticket confusion, enabling Man-in-the-Middle attacks.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 1 Apr 2021
- **Updated:** 14 Oct 2026
- **Also known as:** ALPINE-CVE-2021-22890, CLEANSTART-2026-FP47166, CURL-CVE-2021-22890, DEBIAN-CVE-2021-22890, GHSA-5cwr-528x-3vwc, JLSEC-2025-27, UBUNTU-CVE-2021-22890

## What is CVE-2021-22890?

CVE-2021-22890 is a medium-severity vulnerability in Broadcom Fabric Operating System, published on 1 Apr 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-290 (Authentication Bypass by Spoofing), CWE-300 (Channel Accessible by Non-Endpoint)

## Which versions are affected by CVE-2021-22890?

It affects 11 products.


Products: Broadcom Fabric Operating System, Debian Debian Linux, Fedoraproject Fedora, Haxx Libcurl, Netapp Hci Management Node, Netapp Hci Storage Node, Netapp Solidfire, Oracle Communications Billing and Revenue Management, Oracle Essbase, Siemens Sinec Infrastructure Network Services, Splunk Universal Forwarder.

## How do I fix CVE-2021-22890?

Upgrade to a fixed version.

## Is CVE-2021-22890 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-22890 exists.

## Other vulnerabilities in Broadcom Fabric Operating System

- [CVE-2025-1976](https://insights.sbomify.com/CVE-2025-1976/): Broadcom Brocade Fabric OS Code Injection (high 8.6, exploited in the wild)
- [CVE-2021-22555](https://insights.sbomify.com/CVE-2021-22555/): Linux Kernel Heap Out-of-Bounds Write (high 8.3, exploited in the wild)
- [CVE-2022-33186](https://insights.sbomify.com/CVE-2022-33186/): Command injection in Brocade Fabric OS (critical 9.8)
- [CVE-2021-27797](https://insights.sbomify.com/CVE-2021-27797/): Hardcoded credentials in Brocade Fabric OS (critical 9.8)
- [CVE-2020-15371](https://insights.sbomify.com/CVE-2020-15371/): Code injection in Brocade Fabric OS (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-22890 and fix it if it is affected.

What it is: CVE-2021-22890 is a medium-severity vulnerability in Broadcom Fabric Operating System, published on 1 Apr 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-22890 exists.

Affected product: Broadcom Fabric Operating System. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-22890/ (Markdown: https://insights.sbomify.com/CVE-2021-22890/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-22890
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-22890
- OSV: https://osv.dev/vulnerability/CVE-2021-22890

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-22890/
Summaries are generated and may contain mistakes; the official description above is the record.