CVE-2021-39140: XStream is a simple library to serialize objects to XML and back again

This month

MEDIUM 6.5WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-39140 is a medium-severity flaw (CVSS 6.5) affecting xstream, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability 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. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to

Why this priority

EPSS top 7%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	5.9% (top 7%)
CISA exploited list	No
Weakness	CWE-502, CWE-835
Published	2021-08-23
Last modified	2026-10-07

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

Last updated 2026-10-07 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-08-23 19:15 UTCPublished CVE record published
2026-10-07 21:17 UTCUpdated Record last modified

xstream xstream UPGRADE

Affected: < 1.4.18

Fixed in: 1.4.18

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.4.18 (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.

debian debian linux MITIGATE

Affected: 9.0 · 10.0 · 11.0

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.

fedoraproject fedora MITIGATE

Affected: 33 · 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 33

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.

netapp snapmanager MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

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

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp snapmanager MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

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

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

oracle business activity monitoring DOWNGRADE

Affected: 12.2.1.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.2.1.4.0

1. Check installed version

apt-cache policy business-activity-monitoring || rpm -q business-activity-monitoring || business-activity-monitoring --version

2. No fixed release: DOWNGRADE to a release before 12.2.1.4.0 (Debian / Ubuntu)

apt-cache madison business-activity-monitoring sudo apt install business-activity-monitoring=<VERSION_BEFORE_12.2.1.4.0> sudo apt-mark hold business-activity-monitoring

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

dnf --showduplicates list business-activity-monitoring sudo dnf downgrade business-activity-monitoring-<VERSION_BEFORE_12.2.1.4.0> sudo dnf versionlock add business-activity-monitoring

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.

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-2021-39140?

xstream: upgrade to 1.4.18; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-39140 being exploited?

CVE-2021-39140 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-2021-39140 affect?

CVE-2021-39140 affects xstream, debian linux, fedora. Severity is medium (CVSS 6.5). XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability may allow a remote attacker to allocate 100% CPU time on the target system depending on CPU type or parallel execution of such a

How urgent is CVE-2021-39140?

Priority 56/100. EPSS top 7%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

Debian vulnerabilities

Related CVEs

CVE-2013-7285 CRITICAL 9.8 DOWNGRADE DOWNGRADE Xstream API versions up to 1.4.6 and version 1.4.10, if the security framework has not been initialized, may a
CVE-2021-39153 HIGH 8.5 UPGRADE MITIGATE XStream is a simple library to serialize objects to XML and back again
CVE-2021-39152 HIGH 8.5 UPGRADE MITIGATE XStream is a simple library to serialize objects to XML and back again
CVE-2021-39151 HIGH 8.5 UPGRADE MITIGATE XStream is a simple library to serialize objects to XML and back again
CVE-2021-39150 HIGH 8.5 UPGRADE MITIGATE XStream is a simple library to serialize objects to XML and back again

References

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