Security readout for executives and security teams
Plain-English summary
CVE-2021-43859 affects XStream before 1.4.19, a Java XML serialization library. A remote, unauthenticated attacker could provide specially structured input that makes the target spend excessive CPU, causing denial of service. It does not indicate data theft or code execution in the supplied sources.
Executive priority
Prioritize remediation for externally reachable Java services or critical platforms using vulnerable XStream. The business risk is service outage, not confirmed compromise. Patch through dependency or vendor channels, and track exceptions where NO_REFERENCE mode is used temporarily.
Technical view
The flaw is CWE-400 uncontrolled resource consumption. Vulnerable XStream versions may consume 100% CPU while processing highly recursive collections or maps from the input stream. XStream 1.4.19 adds monitoring of collection element-add time and throws an exception when a threshold is exceeded.
Likely exposure
Exposure is most likely in Java applications, packaged software, or distributions that bundle XStream below 1.4.19 and deserialize XML from external or untrusted sources. Downstream advisories in the bundle include Debian, Fedora, Oracle, and Jenkins-related references, but product-specific impact must be confirmed from each vendor.
Exploitation context
The CVSS vector is network, low complexity, no privileges, and no user interaction, with high availability impact. The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Treat this as a practical denial-of-service risk where vulnerable XML processing is reachable.
Researcher notes
Validation should focus on dependency presence plus reachable XStream XML deserialization. Do not assume every bundled copy is exploitable without an input path. The supplied evidence supports denial of service only, fixed in 1.4.19, with NO_REFERENCE as a documented workaround.
Mitigation direction
- Upgrade XStream to 1.4.19 or later where directly managed.
- Apply vendor package updates for products or distributions bundling XStream.
- If upgrade is blocked, use NO_REFERENCE mode per XStream guidance.
- Review downstream vendor advisories before changing packaged enterprise products.
- Prioritize internet-facing or high-availability services processing XML input.
Validation and detection
- Scan SBOMs and dependency manifests for XStream below 1.4.19.
- Check runtime artifacts for bundled xstream or libxstream-java versions.
- Identify routes, jobs, or integrations that deserialize XML with XStream.
- Confirm vendor-fixed package versions are installed on managed systems.
- Review monitoring for CPU saturation linked to XML-processing services.
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-400: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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 lookupCVE-2021-43859 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
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/x-stream/xstream/security/advisories/GHSA-rmr5-cpv2-vgjfCVE reference · x_refsource_CONFIRM
- https://github.com/x-stream/xstream/commit/e8e88621ba1c85ac3b8620337dd672e0c0c3a846CVE reference · x_refsource_MISC
- https://x-stream.github.io/CVE-2021-43859.htmlCVE reference · x_refsource_MISC
- FEDORA-2022-ad5cf1c0ddCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2022-983a78275cCVE reference · vendor-advisory, x_refsource_FEDORA
- [debian-lts-announce] 20220215 [SECURITY] [DLA 2924-1] libxstream-java security updateCVE reference · mailing-list, x_refsource_MLIST
- https://www.oracle.com/security-alerts/cpuapr2022.htmlCVE reference · x_refsource_MISC
- https://www.oracle.com/security-alerts/cpujul2022.htmlCVE reference · x_refsource_MISC
- https://lists.debian.org/debian-lts-announce/2024/12/msg00023.htmlCVE reference
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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.