CVE-2021-39152 — A Server-Side Forgery Request vulnerability in XStream via HashMap unmarshaling

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

• Documented patch — www.oracle.com (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Debian Debian Linux, Fedoraproject Fedora, Netapp Snapmanager…).
2. Apply the fixed version or the patch documented under Remediation.
3. EPSS ahead of 96% of scored CVEs: prioritize it in the patch queue.
4. Search available logs for exploit probes matching the vulnerability class (insecure deserialization), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-502 · Deserialization of Untrusted Data

Other CVEs with this weakness →

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 11.38%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
• Monitor serialized objects in requests and unexpected processes spawned by the runtime.

Timeline

What happened to this CVE, newest first.

• 2026
• Affected products added · x-stream/xstream
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• Fix documented
  Oct 13, 2026 · NIST National Vulnerability Database
• CVSS changed · 8.5
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Analyzed
  Oct 13, 2026 · NIST National Vulnerability Database
• Record created in this database
  Oct 13, 2026 · NIST National Vulnerability Database
• 2021
• CVE published
  Aug 23, 2021 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

11 on the record

• www.oracle.com/security-alerts/cpujan2022.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpuapr2022.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• security.netapp.com/advisory/ntap-20210923-0003/
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KV
  Mailing List, vendor-advisory, x_refsource_FEDORA, NIST National Vulnerability Database
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPH
  Mailing List, vendor-advisory, x_refsource_FEDORA, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpujul2022.html
  Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXI
  Mailing List, vendor-advisory, x_refsource_FEDORA, NIST National Vulnerability Database
• www.debian.org/security/2021/dsa-5004
  Third Party Advisory, vendor-advisory, x_refsource_DEBIAN, NIST National Vulnerability Database
• github.com/x-stream/xstream/security/advisories/GHSA-xw4p-crpj-vjx2
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• lists.debian.org/debian-lts-announce/2021/09/msg00017.html
  Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
• x-stream.github.io/CVE-2021-39152.html
  Exploit, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database

Elsewhere on this site

Related CVEs (same products)

• High CVE-2026-12996 A use-after-free in OpenVPN 2.6.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows remote... Jul 30, 2026
• High CVE-2026-61164 Improper Access Control in Oracle Commerce Experience Manager Jul 21, 2026
• High CVE-2026-61157 Improper Access Control in Oracle Commerce Experience Manager Jul 21, 2026
• High CVE-2026-61162 Improper Access Control in Oracle Commerce Experience Manager Jul 21, 2026
• High CVE-2026-61158 Improper Access Control in Oracle Commerce Experience Manager Jul 21, 2026
• High CVE-2026-61159 Exposure of Sensitive Information in Oracle Commerce Experience Manager Jul 21, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-39152 is "A Server-Side Forgery Request vulnerability in XStream via HashMap unmarshaling", rated High. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.5 describes technical severity. EPSS 11.38% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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