---
title: "CVE-2021-22901\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2021-22901?format=md
keywords: index, follow
---

# CVE-2021-22901

Publication date 26 May 2021

Last updated 25 August 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**8.1 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2021-22901?format=md#impact-score)

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## Description

curl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability
resulting in already freed memory being used when a TLS 1.3 session ticket
arrives over a connection. A malicious server can use this in rare
unfortunate circumstances to potentially reach remote code execution in the
client. When libcurl at run-time sets up support for TLS 1.3 session
tickets on a connection using OpenSSL, it stores pointers to the transfer
in-memory object for later retrieval when a session ticket arrives. If the
connection is used by multiple transfers (like with a reused HTTP/1.1
connection or multiplexed HTTP/2 connection) that first transfer object
might be freed before the new session is established on that connection and
then the function will access a memory buffer that might be freed. When
using that memory, libcurl might even call a function pointer in the
object, making it possible for a remote code execution if the server could
somehow manage to get crafted memory content into the correct place in
memory.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2021-22901?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| curl | 22.04 LTS jammy | Not affected |
| 21.10 impish | Not affected |
| 21.04 hirsute | Not affected |
| 20.10 groovy | Not affected |
| 20.04 LTS focal | Not affected |
| 18.04 LTS bionic | Not affected |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not affected |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Notes

---

### [mdeslaur](https://launchpad.net/~mdeslaur)

since 7.75.0 only

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

8.1 · High

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | High |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | High |
  | Integrity impact | High |
  | Availability impact | High |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 8.1 · High |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-22901)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2021-22901)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2021-22901)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2021-22901)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2021-22901>