---
title: "CVE-2021-22901: Use After Free | CubePath"
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…"
language: en
source: https://cubepath.com/security/cve/CVE-2021-22901
---

# CVE-2021-22901: Use After Free | CubePath

## 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.

Official description from the CVE record, published by hackerone. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-22901)

## Key data

### EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score

0.63531 (63.5% probability)

Percentile

99.2%

Scores of

Nov 10, 2026

Model

v2026.06.15

### CISA assessment as of Oct 8, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Automatable

yes

Technical impact

total

### Weakness (CWE)

CWE catalog version 5.0.

CWE names: Copyright © 2006-2026, The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CWE license.

- [CWE-416](https://cwe.mitre.org/data/definitions/416.html) Use After Free

## Affected products

Products listed in the CVE record, as the CNA published them.

- https://github.com/curl/curl

  - affected: 7.75.0 through 7.76.1

## References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

- [hackerone.com/reports/1180380](https://hackerone.com/reports/1180380)
- [curl.se/docs/CVE-2021-22901.html](https://curl.se/docs/CVE-2021-22901.html)
- [github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c34…](https://github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c346e9026479)
- [oracle.com//security-alerts/cpujul2021.html](https://www.oracle.com//security-alerts/cpujul2021.html)
- [security.netapp.com/advisory/ntap-20210723-0001](https://security.netapp.com/advisory/ntap-20210723-0001/)
- [oracle.com/security-alerts/cpujan2022.html](https://www.oracle.com/security-alerts/cpujan2022.html)
- [security.netapp.com/advisory/ntap-20210727-0007](https://security.netapp.com/advisory/ntap-20210727-0007/)
- [oracle.com/security-alerts/cpuapr2022.html](https://www.oracle.com/security-alerts/cpuapr2022.html)
- [cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf)
- [cert-portal.siemens.com/productcert/pdf/ssa-732250.pdf](https://cert-portal.siemens.com/productcert/pdf/ssa-732250.pdf)

## Timeline

1. ID reserved Jan 6, 2021
2. Record published Jun 11, 2021
3. Record last updated Oct 14, 2026

## Look up another CVE

## About CubePath

CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection.

[Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection)

Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 20:03 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)