Security readout for executives and security teams
Plain-English summary
XStream versions before 1.4.18 can deserialize manipulated XML in a way that may let an attacker run code. This matters where Java applications process untrusted XStream input. The risk is lower when XStream’s security framework is configured with a narrow type allowlist, as recommended by the project.
Executive priority
Treat as high priority for Java applications or products processing untrusted XML with XStream. Patch or vendor-update exposed systems first, then reduce residual risk by enforcing allowlist-based deserialization controls.
Technical view
CVE-2021-39147 affects x-stream XStream before 1.4.18. It is an unsafe deserialization issue mapped to CWE-502 and CWE-434, with CVSS 3.1 score 8.5. The advisory describes remote arbitrary code execution through crafted processed input, requiring network access, low privileges, high complexity, and no user interaction.
Likely exposure
Exposure is most likely in Java applications or vendor products embedding XStream before 1.4.18, especially where XML input is accepted from users, integrations, queues, or APIs. Systems using a minimal XStream type allowlist are specifically called out as not affected by the project guidance.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability is serious because successful exploitation could affect confidentiality, integrity, and availability, but the CVSS vector indicates high attack complexity and required low privileges.
Researcher notes
The key exposure question is whether the application uses XStream before 1.4.18 without the recommended allowlist. Do not assume all products are affected merely because Java or XML is present; validate the dependency path, input trust boundary, and vendor advisory status.
Mitigation direction
- Upgrade XStream to 1.4.18 or later where directly used.
- Configure XStream’s security framework with a minimal required type allowlist.
- Check vendor advisories for embedded XStream in packaged products.
- Apply relevant Debian, Fedora, Oracle, or NetApp updates where applicable.
- Prioritize externally reachable or integration-facing XML processing paths.
Validation and detection
- Inventory direct and transitive XStream dependencies across Java applications.
- Confirm deployed XStream versions are not below 1.4.18.
- Review whether XStream processes untrusted XML or integration input.
- Verify an explicit minimal type allowlist is configured.
- Check vendor appliances and platforms against their advisory status.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-434: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-39147 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H1.86Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.5HighVector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/x-stream/xstream/security/advisories/GHSA-h7v4-7xg3-hxccCVE reference · x_refsource_CONFIRM
- https://x-stream.github.io/CVE-2021-39147.htmlCVE reference · x_refsource_MISC
- [debian-lts-announce] 20210929 [SECURITY] [DLA 2769-1] libxstream-java security updateCVE reference · mailing-list, x_refsource_MLIST
- FEDORA-2021-fbad11014aCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-d894ca87dcCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-5e376c0ed9CVE reference · vendor-advisory, x_refsource_FEDORA
- DSA-5004CVE reference · vendor-advisory, x_refsource_DEBIAN
- https://www.oracle.com/security-alerts/cpujan2022.htmlCVE reference · x_refsource_MISC
- https://security.netapp.com/advisory/ntap-20210923-0003/CVE reference · x_refsource_CONFIRM
- https://www.oracle.com/security-alerts/cpuapr2022.htmlCVE reference · x_refsource_MISC
- https://www.oracle.com/security-alerts/cpujul2022.htmlCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Unrestricted Upload of File with Dangerous Type
Unrestricted Upload of File with Dangerous Type represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.