# What is CVE-2021-3711?

> CVE-2021-3711 is a critical-severity flaw (CVSS 9.8) in OpenSSL, published on 24 August 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 88%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-3711

## 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:** 71 out of 100 (High); action: Patch now. Kept up to date as the evidence changes.
- **Severity:** Critical (CVSS 9.8 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:** 88% (latest exploit-likelihood forecast)
- **Published:** 24 August 2021
- **Record last updated:** 21 June 2024
- **Main product:** OpenSSL
- **Affected products:** 31

## What is CVE-2021-3711? 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

In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).

### What kind of flaw is it?

- CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Easy: no special conditions
- 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:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Is CVE-2021-3711 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 88%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 88%, 88%, 88%, 88%, 88%, 88%, 88%.

### Timeline

- 24 August 2021: Published
- 21 June 2024: Record last updated
- 19 November 2025: Exploit likelihood jumped
- 22 November 2025: Exploit likelihood fell

### How Precursor Intelligence ranks it

CVE-2021-3711 scores **71 out of 100 (High)**, with the action "Patch now".

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-2021-3711?

The published record lists 31 products. Versions are as published: "1.1.1 to before 1.1.1l" means from 1.1.1 up to, but not including, 1.1.1l.

- [OpenSSL](https://www.precursorintelligence.com/product/openssl/openssl) by [OpenSSL](https://www.precursorintelligence.com/vendors/openssl) (Application): 1.1.1 to before 1.1.1l
- [Peoplesoft Enterprise Peopletools](https://www.precursorintelligence.com/product/oracle/peoplesoft_enterprise_peopletools) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.57, 8.58, 8.59
- [Communications Session Border Controller](https://www.precursorintelligence.com/product/oracle/communications_session_border_controller) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.4, 9.0
- [Communications Unified Session Manager](https://www.precursorintelligence.com/product/oracle/communications_unified_session_manager) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.2.5, 8.4.5
- [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 10.0, 11.0
- [Enterprise Communications Broker](https://www.precursorintelligence.com/product/oracle/enterprise_communications_broker) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 3.2.0, 3.3.0
- [Enterprise Session Border Controller](https://www.precursorintelligence.com/product/oracle/enterprise_session_border_controller) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.4, 9.0
- [Essbase](https://www.precursorintelligence.com/product/oracle/essbase) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): before 11.1.2.4.47, 21.1 to before 21.3
- [Health Sciences Inform Publisher](https://www.precursorintelligence.com/product/oracle/health_sciences_inform_publisher) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 6.2.1.1, 6.3.1.1
- [Mysql Server](https://www.precursorintelligence.com/product/oracle/mysql_server) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 5.7.0 to 5.7.35, 8.0.0 to 8.0.26
- [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
- [Clustered Data Ontap](https://www.precursorintelligence.com/product/netapp/clustered_data_ontap) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Clustered Data Ontap Antivirus Connector](https://www.precursorintelligence.com/product/netapp/clustered_data_ontap_antivirus_connector) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Communications Cloud Native Core Security Edge Protection Proxy](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_security_edge_protection_proxy) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.7.0
- [Communications Cloud Native Core Unified Data Repository](https://www.precursorintelligence.com/product/oracle/communications_cloud_native_core_unified_data_repository) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 1.15.0
- [E-Series Santricity OS Controller](https://www.precursorintelligence.com/product/netapp/e-series_santricity_os_controller) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): 11.0 to 11.50.2
- [Hci Management Node](https://www.precursorintelligence.com/product/netapp/hci_management_node) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Jd Edwards Enterpriseone Tools](https://www.precursorintelligence.com/product/oracle/jd_edwards_enterpriseone_tools) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): before 9.2.6.3
- [Jd Edwards World Security](https://www.precursorintelligence.com/product/oracle/jd_edwards_world_security) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): a9.4
- [Manageability Software Development Kit](https://www.precursorintelligence.com/product/netapp/manageability_software_development_kit) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Mysql Connectors](https://www.precursorintelligence.com/product/oracle/mysql_connectors) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): up to 8.0.27
- [Mysql Enterprise Monitor](https://www.precursorintelligence.com/product/oracle/mysql_enterprise_monitor) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): up to 8.0.25
- [Nessus Network Monitor](https://www.precursorintelligence.com/product/tenable/nessus_network_monitor) by [Tenable](https://www.precursorintelligence.com/vendors/tenable) (Application): up to 5.13.1
- [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
- [Santricity Smi-S Provider](https://www.precursorintelligence.com/product/netapp/santricity_smi-s_provider) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Snapcenter](https://www.precursorintelligence.com/product/netapp/snapcenter) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Solidfire](https://www.precursorintelligence.com/product/netapp/solidfire) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Storage Encryption](https://www.precursorintelligence.com/product/netapp/storage_encryption) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Tenable.sc](https://www.precursorintelligence.com/product/tenable/tenable.sc) by [Tenable](https://www.precursorintelligence.com/vendors/tenable) (Application): 5.16.0 to 5.19.1
- [Zfs Storage Appliance Kit](https://www.precursorintelligence.com/product/oracle/zfs_storage_appliance_kit) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.8

## How do I fix CVE-2021-3711?

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

- [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)
- [oracle.com](https://www.oracle.com/security-alerts/cpuoct2021.html) (Patch, Third-party advisory)
- [openssl.org](https://www.openssl.org/news/secadv/20210824.txt) (Vendor advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2021/08/26/2) (Mailing list, Third-party advisory)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf) (Third-party advisory)
- [git.openssl.org](https://git.openssl.org/gitweb/?p=openssl.git%3Ba=commitdiff%3Bh=59f5e75f3bced8fc0e130d72a3f582cf7b480b46)
- [lists.apache.org](https://lists.apache.org/thread.html/r18995de860f0e63635f3008fd2a6aca82394249476d21691e7c59c9e%40%3Cdev.tomcat.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rad5d9f83f0d11fb3f8bb148d179b8a9ad7c6a17f18d70e5805a713d1%40%3Cdev.tomcat.apache.org%3E)
- [security.gentoo.org](https://security.gentoo.org/glsa/202209-02) (Third-party advisory)
- [security.gentoo.org](https://security.gentoo.org/glsa/202210-02) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20210827-0010/) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20211022-0003/) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20240621-0006/)
- [debian.org](https://www.debian.org/security/2021/dsa-4963) (Third-party advisory)
- [tenable.com](https://www.tenable.com/security/tns-2021-16) (Third-party advisory)
- [tenable.com](https://www.tenable.com/security/tns-2022-02) (Third-party advisory)

## Questions

### What is CVE-2021-3711?

CVE-2021-3711 is a critical-severity flaw in OpenSSL, published on 24 August 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-2021-3711?

It scores 9.8 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2021-3711 is 71 out of 100, which is High. Its action is "Patch now". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2021-3711 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 88%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2021-3711 affect?

For OpenSSL: 1.1.1 to before 1.1.1l. The record lists 31 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2021-3711?

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-2021-3711 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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