CVE-2021-43859: XStream is an open source java library to serialize objects to XML and back again

Q: How do I fix CVE-2021-43859?

jenkins: upgrade to 2.319.3, 2.334; xstream: upgrade to 1.4.19; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-43859 being exploited?

CVE-2021-43859 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-43859 affect?

CVE-2021-43859 affects jenkins, xstream, fedora. Severity is high (CVSS 7.5). XStream is an open source java library to serialize objects to XML and back again. Versions prior to 1.4.19 may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a pay

Q: How urgent is CVE-2021-43859?

Priority 65/100. High severity; EPSS top 5%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

This week

HIGH 7.5REMOTEWATCHLISTUPGRADEUPGRADEMITIGATE

CVE-2021-43859 is a high-severity flaw (CVSS 7.5) affecting jenkins, xstream, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XStream is an open source java library to serialize objects to XML and back again. Versions prior to 1.4.19 may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a payload resulting in a denial of service only by manipulating the processed input stream. XStream 1.4.19 monitors and accumulates the time it takes to add elements to collections and throws an exception if a set t

Why this priority

High severity
EPSS top 5%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	7.9% (top 5%)
CISA exploited list	No
Weakness	CWE-400
Published	2022-02-01
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: debian · fedoraproject · jenkins · oracle · xstream

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-02-01 12:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

jenkins jenkins UPGRADE

Affected: < 2.319.3 · >= 2.321 and < 2.334

Fixed in: 2.319.3, 2.334

Safe to downgrade to: a release before 2.321

1. Check installed version

apt-cache policy jenkins || rpm -q jenkins || jenkins --version

2. UPGRADE to 2.319.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade jenkins

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade jenkins

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.321 (Debian / Ubuntu)

apt-cache madison jenkins sudo apt install jenkins=<VERSION_BEFORE_2.321> sudo apt-mark hold jenkins

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list jenkins sudo dnf downgrade jenkins-<VERSION_BEFORE_2.321> sudo dnf versionlock add jenkins

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

xstream xstream UPGRADE

Affected: < 1.4.19

Fixed in: 1.4.19

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy xstream || rpm -q xstream || xstream --version

2. UPGRADE to 1.4.19 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade xstream

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade xstream

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

oracle commerce guided search DOWNGRADE

Affected: 11.3.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.3.2

1. Check installed version

apt-cache policy commerce-guided-search || rpm -q commerce-guided-search || commerce-guided-search --version

2. No fixed release: DOWNGRADE to a release before 11.3.2 (Debian / Ubuntu)

apt-cache madison commerce-guided-search sudo apt install commerce-guided-search=<VERSION_BEFORE_11.3.2> sudo apt-mark hold commerce-guided-search

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list commerce-guided-search sudo dnf downgrade commerce-guided-search-<VERSION_BEFORE_11.3.2> sudo dnf versionlock add commerce-guided-search

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

oracle communications brm - elastic charging engine UPGRADE

Affected: < 12.0.0.4.6 · 12.0.0.5.0

Fixed in: 12.0.0.4.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy communications-brm---elastic-charging-engine || rpm -q communications-brm---elastic-charging-engine || communications-brm---elastic-charging-engine --version

2. UPGRADE to 12.0.0.4.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade communications-brm---elastic-charging-engine

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade communications-brm---elastic-charging-engine

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-43859?

jenkins: upgrade to 2.319.3, 2.334; xstream: upgrade to 1.4.19; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-43859 being exploited?

CVE-2021-43859 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-43859 affect?

CVE-2021-43859 affects jenkins, xstream, fedora. Severity is high (CVSS 7.5). XStream is an open source java library to serialize objects to XML and back again. Versions prior to 1.4.19 may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a pay

How urgent is CVE-2021-43859?

Priority 65/100. High severity; EPSS top 5%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Java vulnerabilities · Jenkins vulnerabilities · Debian vulnerabilities

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References

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