Medium Injection exploit reference

CVE-2020-26259 — XStream is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling. The vulnerability may allow a remote attacker to delete arbitrary know files on the host as log as the executing process has sufficient rights only by manipulating the processed input stream. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.15. The reported vulnerability does not exist running Java 15 or higher. No user is affected, who followed the recommendation to setup XStream's Security Framework with a whitelist! Anyone relying on XStream's default blacklist can immediately switch to a whilelist for the allowed types to avoid the vulnerability. Users of XStream 1.4.14 or below who still want to use XStream default blacklist can use a workaround described in more detailed in the referenced advisories.

Published Dec 15, 2020 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 82.4% (30-day exploitation probability)+15
Technical severity (medium)+3
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

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

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

82.39%

ahead of 100% of scored CVEs · Oct 14, 2026

Affects

Apache Software Foundation

Struts and 3 more

CVSS base

6.8

Medium · 3 source(s)

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.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

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

Documented mitigation — github.com (NIST National Vulnerability Database)
Documented mitigation — x-stream.github.io (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.

Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Struts, Debian Debian Linux, Fedoraproject Fedora…).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
Apply the documented mitigations until a definitive fix is available.
EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
Search available logs for exploit probes matching the vulnerability class (injection), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Apache Software Foundation	Struts	< 6.0.0	Vulnerable	NIST National Vulnerability Database
Debian	Debian Linux	version 9.0version 10.0	Vulnerable	NIST National Vulnerability Database
Fedoraproject	Fedora	version 33version 34version 35	Vulnerable	NIST National Vulnerability Database
Xstream	Xstream	< 1.4.15	Vulnerable	NIST National Vulnerability Database
Xstream	Xstream	version < 1.4.15	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

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

Attack vector

Network

Attack complexity

High

Privileges required

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

High

Availability

None

Every base score collected

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

Score	Version	Severity	Expl.	Impact	Scored by
6.8	CVSS 3.1	Medium	2.2	4.0	security-advisories@github.com via NIST National Vulnerability Database
6.8	CVSS 3.1	Medium	2.2	4.0	nvd@nist.gov via NIST National Vulnerability Database
6.8	CVSS 3.1	Medium	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP
6.4	CVSS 2.0	Medium	10.0	4.9	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-78 · OS Command Injection

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 82.39%

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).
Look for parameters with command/query metacharacters and unexpected child processes of the service.

web/proxy/WAF logsnetwork IDS/IPSapplication logsendpoint telemetry (EDR)

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 · 6.8
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
2020
CVE published
Dec 15, 2020 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

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

References

9 on the record

x-stream.github.io/CVE-2020-26259.html
Exploit, Mitigation, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
github.com/x-stream/xstream/security/advisories/GHSA-jfvx-7wrx-43fh
Mitigation, 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
lists.debian.org/debian-lts-announce/2020/12/msg00042.html
Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34
Issue Tracking, Mailing List, mailing-list, x_refsource_MLIST, 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-4828
Third Party Advisory, vendor-advisory, x_refsource_DEBIAN, NIST National Vulnerability Database
security.netapp.com/advisory/ntap-20210409-0005/
Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor

Injection
same class

CWE-78
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-104711 Apache Struts: OGNL injection in the legacy RESTful action mapper 10d
High CVE-2026-104712 Apache Struts: Disproportionate response size when rendering BigDecimal request parameters 10d
Medium CVE-2026-104713 Apache Struts: Unbounded request body read in the REST plugin 10d
High CVE-2026-104714 Apache Struts: Shared message formatter exposes date and time values across concurrent requests 10d
High CVE-2026-73635 Allocation of Resources Without Limits or Throttling in Apache Software Foundation Struts Aug 15, 2026
High CVE-2026-73634 Uncontrolled Resource Consumption in Apache Software Foundation Struts Aug 15, 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-2020-26259 is "XStream is vulnerable to an Arbitrary File Deletion on the local host when unmarshalling", rated Medium. It affects Struts (Apache Software Foundation); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.8 describes technical severity. EPSS 82.39% 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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