# What is CVE-2021-3518?

> CVE-2021-3518 is a high-severity flaw (CVSS 8.8) in Libxml2 from Xmlsoft, published on 18 May 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 22%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-3518

## 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:** 49 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 8.8 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:** 22% (latest exploit-likelihood forecast)
- **Published:** 18 May 2021
- **Record last updated:** 7 November 2023
- **Main product:** Libxml2 from Xmlsoft
- **Affected products:** 19

## What is CVE-2021-3518? In plain terms

It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. If it works, the attacker can read data, change data and take it offline.

### The official description

There's a flaw in libxml2 in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by an application linked with libxml2 could trigger a use-after-free. The greatest impact from this flaw is to confidentiality, integrity, and availability.

### 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: Easy: no special conditions
- Login needed first: No login needed
- Does someone have to click: Yes, a person has to take an action
- 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:R/S:U/C:H/I:H/A:H`

## Is CVE-2021-3518 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 22%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 22%, 22%, 22%, 22%, 22%, 22%, 22%.

### Timeline

- 18 May 2021: Published
- 7 November 2023: Record last updated
- 25 September 2026: Exploit likelihood jumped

### How Precursor Intelligence ranks it

CVE-2021-3518 scores **49 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-2021-3518?

The published record lists 19 products. Versions are as published: "before 2.9.11" means every version up to, but not including, 2.9.11.

- [Libxml2](https://www.precursorintelligence.com/product/xmlsoft/libxml2) by [Xmlsoft](https://www.precursorintelligence.com/vendors/xmlsoft) (Application): before 2.9.11
- [Enterprise Manager Base Platform](https://www.precursorintelligence.com/product/oracle/enterprise_manager_base_platform) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 13.4.0.0, 13.5.0.0
- [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 33, 34
- [Real User Experience Insight](https://www.precursorintelligence.com/product/oracle/real_user_experience_insight) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 13.4.1.0, 13.5.1.0
- [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 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
- [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 9.0
- [Enterprise Linux](https://www.precursorintelligence.com/product/redhat/enterprise_linux) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.0
- [Enterprise Manager Ops Center](https://www.precursorintelligence.com/product/oracle/enterprise_manager_ops_center) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 12.4.0.0
- [Hci H410c](https://www.precursorintelligence.com/product/netapp/hci_h410c) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Hardware): version not specified
- [Hci H410c Firmware](https://www.precursorintelligence.com/product/netapp/hci_h410c_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [Jboss Core Services](https://www.precursorintelligence.com/product/redhat/jboss_core_services) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): version not specified
- [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 Workbench](https://www.precursorintelligence.com/product/oracle/mysql_workbench) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): up to 8.0.26
- [Ontap Select Deploy Administration Utility](https://www.precursorintelligence.com/product/netapp/ontap_select_deploy_administration_utility) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Peoplesoft Enterprise Peopletools](https://www.precursorintelligence.com/product/oracle/peoplesoft_enterprise_peopletools) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 8.58
- [Snapdrive](https://www.precursorintelligence.com/product/netapp/snapdrive) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified

## How do I fix CVE-2021-3518?

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

- [bugzilla.redhat.com](https://bugzilla.redhat.com/show_bug.cgi?id=1954242) (Issue tracking, 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/cpuoct2021.html) (Patch, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2021/Jul/54) (Mailing list, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2021/Jul/55) (Mailing list, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2021/Jul/58) (Mailing list, Third-party advisory)
- [seclists.org](http://seclists.org/fulldisclosure/2021/Jul/59) (Mailing list, Third-party advisory)
- [lists.apache.org](https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E)
- [lists.apache.org](https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2021/05/msg00008.html) (Mailing list, Third-party advisory)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BZOMV5J4PMZAORVT64BKLV6YIZAFDGX6/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QVM4UJ3376I6ZVOYMHBNX4GY3NIV52WV/)
- [security.gentoo.org](https://security.gentoo.org/glsa/202107-05) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20210625-0002/) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT212601) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT212602) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT212604) (Third-party advisory)
- [support.apple.com](https://support.apple.com/kb/HT212605) (Third-party advisory)
- [oracle.com](https://www.oracle.com/security-alerts/cpujul2022.html) (Not applicable)

## Questions

### What is CVE-2021-3518?

CVE-2021-3518 is a high-severity flaw in Libxml2 from Xmlsoft, published on 18 May 2021. It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. If it works, the attacker can read data, change data and take it offline.

### How serious is CVE-2021-3518?

It scores 8.8 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2021-3518 is 49 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-2021-3518 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 22%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2021-3518 affect?

For Libxml2 from Xmlsoft: before 2.9.11. The record lists 19 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2021-3518?

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-2021-3518 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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