Security readout for executives and security teams
Plain-English summary
XStream versions before 1.4.18 can let an attacker run code if an application processes malicious XML through XStream. The risk is highest where XML input is externally controlled and the recommended whitelist security framework was not used.
Executive priority
Prioritize remediation for internet-facing services, upload workflows, integrations, or products that process XML with XStream. Treat as high severity, but not confirmed actively exploited from the provided sources.
Technical view
CVE-2021-39145 affects x-stream XStream before 1.4.18. Sources describe arbitrary code execution by manipulating the processed input stream, with CVSS 8.5, network attack vector, high complexity, low privileges, and no user interaction. XStream 1.4.18 changed away from a default blacklist model.
Likely exposure
Applications or products using XStream before 1.4.18 are exposed when they deserialize attacker-controlled XML and lack a strict whitelist of permitted types. Exposure may also exist through packaged dependencies such as libxstream-java or vendor products listed in advisories.
Exploitation context
The source bundle does not show CISA KEV listing or other cited evidence of active exploitation. The advisory describes remote code execution potential, but exploitation depends on application use, input control, and absent or insufficient XStream security whitelisting.
Researcher notes
Focus analysis on unsafe deserialization paths, whitelist configuration, and dependency provenance. The sources indicate users following the whitelist recommendation are not affected, but evidence is incomplete for each downstream vendor product without checking vendor-specific advisories.
Mitigation direction
- Upgrade XStream to 1.4.18 or a vendor-fixed package.
- Apply Debian, Fedora, Oracle, or NetApp guidance where their products package XStream.
- Configure XStream security with a minimal required type whitelist.
- Avoid deserializing untrusted XML through XStream where possible.
- Check vendor guidance if XStream is embedded in third-party software.
Validation and detection
- Inventory direct and transitive XStream dependencies across Java builds and deployed packages.
- Confirm no runtime uses XStream versions before 1.4.18.
- Review XStream initialization for a strict minimal type whitelist.
- Trace whether processed XML streams can be controlled by external users.
- Check vendor advisories for appliances or platforms bundling XStream.
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-2021-39145 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-8jrj-525p-826vCVE reference · x_refsource_CONFIRM
- https://x-stream.github.io/CVE-2021-39145.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.