CVE-2021-29505: XStream is software for serializing Java objects to XML and back again

Q: How do I fix CVE-2021-29505?

xstream: upgrade to 1.4.17; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-29505 being exploited?

CVE-2021-29505 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-2021-29505 affect?

CVE-2021-29505 affects xstream, debian linux, fedora. Severity is high (CVSS 7.5). XStream is software for serializing Java objects to XML and back again. A vulnerability in XStream versions prior to 1.4.17 may allow a remote attacker has sufficient rights to execute commands of the host only by manipulating the processed

Q: How urgent is CVE-2021-29505?

Priority 56/100. High severity; EPSS top 1%: very likely to be exploited; On your watchlist

This week

HIGH 7.5WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-29505 is a high-severity flaw (CVSS 7.5) 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 software for serializing Java objects to XML and back again. A vulnerability in XStream versions prior to 1.4.17 may allow a remote attacker has sufficient rights to execute commands of the host only by manipulating the processed input stream. No user who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types is affected. The vulnerability is patched in version 1.4.17.

Why this priority

High severity
EPSS top 1%: very likely to be exploited
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	77.2% (top 1%)
CISA exploited list	No
Weakness	CWE-94, CWE-502
Published	2021-05-28
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

2021-05-28 21:15 UTCPublished CVE record published
2026-10-07 21:17 UTCUpdated Record last modified

xstream xstream UPGRADE

Affected: < 1.4.17

Fixed in: 1.4.17

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.4.17 (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 banking cash management DOWNGRADE

Affected: 14.2 · 14.3 · 14.5

Fixed in: no fixed release known

Safe to downgrade to: a release before 14.2

1. Check installed version

apt-cache policy banking-cash-management || rpm -q banking-cash-management || banking-cash-management --version

2. No fixed release: DOWNGRADE to a release before 14.2 (Debian / Ubuntu)

apt-cache madison banking-cash-management sudo apt install banking-cash-management=<VERSION_BEFORE_14.2> sudo apt-mark hold banking-cash-management

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

dnf --showduplicates list banking-cash-management sudo dnf downgrade banking-cash-management-<VERSION_BEFORE_14.2> sudo dnf versionlock add banking-cash-management

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: XStream <1.4.17 - Remote Code Execution

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-2021-29505?

xstream: upgrade to 1.4.17; 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-2021-29505 being exploited?

CVE-2021-29505 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-2021-29505 affect?

CVE-2021-29505 affects xstream, debian linux, fedora. Severity is high (CVSS 7.5). XStream is software for serializing Java objects to XML and back again. A vulnerability in XStream versions prior to 1.4.17 may allow a remote attacker has sufficient rights to execute commands of the host only by manipulating the processed

How urgent is CVE-2021-29505?

Priority 56/100. High severity; EPSS top 1%: very likely to be exploited; On your watchlist

Software pages

Java vulnerabilities · 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

← Back to latest CVEs