CVE intelligence and bounded remediation

CVE-2021-39144 — XStream Remote Code Execution Vulnerability

High CVSS 8.5 CISA KEV

XStream is a simple library to serialize objects to XML and back again. In affected versions this vulnerability may allow a remote attacker has sufficient rights to execute commands of the 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. XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose.

Severity
High
CVSS
8.5 (3.1)
Published
2021-08-23
CISA KEV
Known exploited
Ecosystem
software/application
Weaknesses
CWE-94, CWE-502, CWE-306

Affected products

  • xstream / xstream
  • debian / debian_linux / 9.0
  • debian / debian_linux / 10.0
  • debian / debian_linux / 11.0
  • fedoraproject / fedora / 33
  • fedoraproject / fedora / 34

Showing 6 representative product identities from 36 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Command, code, expression, and template injection

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace untrusted values to process execution, interpreters, evaluators, template engines, dynamic imports, and administrative scripting features.
  • Determine whether the affected path is reachable across each trust boundary and which service account or host privilege it inherits.
  • Review configuration for optional execution features, unsafe compatibility modes, and shell invocation.

Remediate safely

  • Replace string-built commands or evaluated code with fixed operations and structured argument APIs that do not invoke a shell.
  • Use strict allowlists for operation identifiers and reject unexpected input before it reaches any interpreter.
  • Update the affected component and add inert regression tests covering metacharacters, encoding variants, and alternate request paths.

Authoritative sources

Complete CVE record and remediation plan

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