# What is CVE-2021-21346?

> CVE-2021-21346 is a critical-severity flaw (CVSS 9.8) in Xstream, published on 23 March 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 76%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-21346

## 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:** 72 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:** 76% (latest exploit-likelihood forecast)
- **Published:** 23 March 2021
- **Record last updated:** 23 May 2025
- **Main product:** Xstream
- **Affected products:** 16

## What is CVE-2021-21346? 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

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.16, there is a vulnerability which may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.16.

### What kind of flaw is it?

- CWE-434: Unrestricted Upload of File with Dangerous Type
- CWE-502: Deserialization of Untrusted Data

### 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-2021-21346 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 76%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 76%, 76%, 76%, 76%, 76%, 76%, 76%.

### Timeline

- 23 March 2021: Published
- 23 May 2025: Record last updated
- 19 November 2025: Exploit likelihood jumped
- 22 November 2025: Exploit likelihood fell

### How Precursor Intelligence ranks it

CVE-2021-21346 scores **72 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-2021-21346?

The published record lists 16 products. Versions are as published: "before 1.4.16" means every version up to, but not including, 1.4.16.

- [Xstream](https://www.precursorintelligence.com/product/xstream/xstream) by [Xstream](https://www.precursorintelligence.com/vendors/xstream) (Application): before 1.4.16
- [Communications Unified Inventory Management](https://www.precursorintelligence.com/product/oracle/communications_unified_inventory_management) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 7.3.2, 7.3.4, 7.3.5, 7.4.0, 7.4.1
- [Banking Platform](https://www.precursorintelligence.com/product/oracle/banking_platform) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 2.4.0, 2.7.1, 2.9.0, 2.12.0
- [Retail Xstore Point of Service](https://www.precursorintelligence.com/product/oracle/retail_xstore_point_of_service) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 16.0.6, 17.0.4, 18.0.3, 19.0.2
- [Activemq](https://www.precursorintelligence.com/product/apache/activemq) by [Apache](https://www.precursorintelligence.com/vendors/apache) (Application): before 5.15.14, 5.16.0, 5.16.1
- [Banking Virtual Account Management](https://www.precursorintelligence.com/product/oracle/banking_virtual_account_management) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 14.2.0, 14.3.0, 14.5.0
- [Bi Publisher](https://www.precursorintelligence.com/product/oracle/bi_publisher) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 5.5.0.0.0, 12.2.1.3.0, 12.2.1.4.0
- [Business Activity Monitoring](https://www.precursorintelligence.com/product/oracle/business_activity_monitoring) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 11.1.1.9.0, 12.2.1.3.0, 12.2.1.4.0
- [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 9.0, 10.0, 11.0
- [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 33, 34, 35
- [Webcenter Portal](https://www.precursorintelligence.com/product/oracle/webcenter_portal) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 11.1.1.9.0, 12.2.1.3.0, 12.2.1.4.0
- [Banking Enterprise Default Management](https://www.precursorintelligence.com/product/oracle/banking_enterprise_default_management) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 2.10.0, 2.12.0
- [Communications Billing and Revenue Management Elastic Charging Engine](https://www.precursorintelligence.com/product/oracle/communications_billing_and_revenue_management_elastic_charging_engine) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 12.0.0.3.0
- [Communications Policy Management](https://www.precursorintelligence.com/product/oracle/communications_policy_management) by [Oracle](https://www.precursorintelligence.com/vendors/oracle) (Application): 12.5.0
- [Jmeter](https://www.precursorintelligence.com/product/apache/jmeter) by [Apache](https://www.precursorintelligence.com/vendors/apache) (Application): before 5.5
- [Oncommand Insight](https://www.precursorintelligence.com/product/netapp/oncommand_insight) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified

## How do I fix CVE-2021-21346?

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/cpujan2022.html) (Patch, Vendor advisory)
- [x-stream.github.io](https://x-stream.github.io/security.html#workaround) (Mitigation, Third-party advisory)
- [x-stream.github.io](http://x-stream.github.io/changes.html#1.4.16) (Release notes, Third-party advisory)
- [github.com](https://github.com/x-stream/xstream/security/advisories/GHSA-4hrm-m67v-5cxr) (Third-party advisory)
- [lists.apache.org](https://lists.apache.org/thread.html/r8244fd0831db894d5e89911ded9c72196d395a90ae655414d23ed0dd%40%3Cusers.activemq.apache.org%3E) (Third-party advisory, Issue tracking, Mailing list)
- [lists.apache.org](https://lists.apache.org/thread.html/r9ac71b047767205aa22e3a08cb33f3e0586de6b2fac48b425c6e16b0%40%3Cdev.jmeter.apache.org%3E) (Third-party advisory, Issue tracking, Mailing list)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2021/04/msg00002.html) (Mailing list, Third-party advisory)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/) (Third-party advisory, Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/) (Third-party advisory, Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/) (Third-party advisory, Mailing list)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20210430-0002/) (Third-party advisory)
- [debian.org](https://www.debian.org/security/2021/dsa-5004) (Third-party advisory, Mailing list)
- [oracle.com](https://www.oracle.com//security-alerts/cpujul2021.html) (Third-party advisory)
- [oracle.com](https://www.oracle.com/security-alerts/cpuoct2021.html) (Third-party advisory)
- [x-stream.github.io](https://x-stream.github.io/CVE-2021-21346.html) (Exploit, Third-party advisory)

## Questions

### What is CVE-2021-21346?

CVE-2021-21346 is a critical-severity flaw in Xstream, published on 23 March 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-2021-21346?

It scores 9.8 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2021-21346 is 72 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-2021-21346 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 76%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2021-21346 affect?

For Xstream: before 1.4.16. The record lists 16 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2021-21346?

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-2021-21346 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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