# What is CVE-2021-22901?

> CVE-2021-22901 is a high-severity flaw (CVSS 8.1) in Curl from Haxx, published on 11 June 2021. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 64%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-22901

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 65 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 8.1 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 64% (latest exploit-likelihood forecast)
- **Published:** 11 June 2021
- **Record last updated:** 27 March 2024
- **Main product:** Curl from Haxx
- **Affected products:** 34

## What is CVE-2021-22901? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### The official 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.

### What kind of flaw is it?

- CWE-416: Use After Free

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Hard: conditions must line up
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can read data, change data and take it offline

Severity vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Is CVE-2021-22901 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 64%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 60%, 60%, 60%, 60%, 64%, 64%, 64%.

### Timeline

- 11 June 2021: Published
- 27 March 2024: Record last updated
- 16 June 2026: Exploit likelihood jumped

### How Precursor Intelligence ranks it

CVE-2021-22901 scores **65 out of 100 (Medium)**, with the action "Plan remediation".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2021-22901?

The published record lists 34 products. Versions are as published: "8.2.0 to before 8.2.12" means from 8.2.0 up to, but not including, 8.2.12.

- [Curl](https://www.precursorintelligence.com/product/haxx/curl) by [Haxx](https://www.precursorintelligence.com/vendors/haxx) (Application): 7.75.0 to 7.76.1
- [Universal Forwarder](https://www.precursorintelligence.com/product/splunk/universal_forwarder) by [Splunk](https://www.precursorintelligence.com/vendors/splunk) (Application): 8.2.0 to before 8.2.12, 9.0.0 to before 9.0.6, 9.1.0
- [Communications Cloud Native Core Network Repository Function](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_network_repository_function) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.15.0, 1.15.1
- [Essbase](https://www.precursorintelligence.com/product/oracle/essbase) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): before 11.1.2.4.047, 21.0 to before 21.3
- [Mysql Server](https://www.precursorintelligence.com/product/oracle/mysql_server) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): up to 5.7.34, 8.0.0 to 8.0.25
- [Active Iq Unified Manager](https://www.precursorintelligence.com/product/netapp/active_iq_unified_manager) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Cloud Backup](https://www.precursorintelligence.com/product/netapp/cloud_backup) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Communications Cloud Native Core Binding Support Function](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_binding_support_function) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.11.0
- [Communications Cloud Native Core Network Function Cloud Native Environment](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_network_function_cloud_native_environment) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.10.0
- [Communications Cloud Native Core Network Slice Selection Function](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_network_slice_selection_function) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.8.0
- [Communications Cloud Native Core Service Communication Proxy](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_service_communication_proxy) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.15.0
- [H300e](https://www.precursorintelligence.com/product/netapp/h300e) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H300e Firmware](https://www.precursorintelligence.com/product/netapp/h300e_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H300s](https://www.precursorintelligence.com/product/netapp/h300s) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H300s Firmware](https://www.precursorintelligence.com/product/netapp/h300s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H410s](https://www.precursorintelligence.com/product/netapp/h410s) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H410s Firmware](https://www.precursorintelligence.com/product/netapp/h410s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H500e](https://www.precursorintelligence.com/product/netapp/h500e) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H500e Firmware](https://www.precursorintelligence.com/product/netapp/h500e_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H500s](https://www.precursorintelligence.com/product/netapp/h500s) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H500s Firmware](https://www.precursorintelligence.com/product/netapp/h500s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H700e](https://www.precursorintelligence.com/product/netapp/h700e) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H700e Firmware](https://www.precursorintelligence.com/product/netapp/h700e_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H700s](https://www.precursorintelligence.com/product/netapp/h700s) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [H700s Firmware](https://www.precursorintelligence.com/product/netapp/h700s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [Hci Compute Node](https://www.precursorintelligence.com/product/netapp/hci_compute_node) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [Hci Compute Node Firmware](https://www.precursorintelligence.com/product/netapp/hci_compute_node_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [Oncommand Insight](https://www.precursorintelligence.com/product/netapp/oncommand_insight) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Oncommand Workflow Automation](https://www.precursorintelligence.com/product/netapp/oncommand_workflow_automation) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Sinec Infrastructure Network Services](https://www.precursorintelligence.com/product/siemens/sinec_infrastructure_network_services) by [Siemens](https://www.precursorintelligence.com/vendors/siemens) (Application): before 1.0.1.1
- [Snapcenter](https://www.precursorintelligence.com/product/netapp/snapcenter) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- Solidfire & Hci Management Node by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Solidfire Baseboard Management Controller Firmware](https://www.precursorintelligence.com/product/netapp/solidfire_baseboard_management_controller_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- Solidfire, Enterprise Sds & Hci Storage Node by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified

## How do I fix CVE-2021-22901?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

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

## Questions

### What is CVE-2021-22901?

CVE-2021-22901 is a high-severity flaw in Curl from Haxx, published on 11 June 2021. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### How serious is CVE-2021-22901?

It scores 8.1 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2021-22901 is 65 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2021-22901 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 64%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2021-22901 affect?

For Curl from Haxx: 7.75.0 to 7.76.1. The record lists 34 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2021-22901?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2021-22901 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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