CVE-2020-26258 | Server-Side Forgery Request can be activated unmarshalling with XStream

Exp

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, a Server-Side Forgery Request vulnerability can be activated when unmarshalling. The vulnerability may allow a remote attacker to request data from internal resources that are not publicly available 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 if 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: 2020-12-15 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-26258 is rated High Exploit Risk (70.1/100): CVSS Medium severity, with high exploitation likelihood (EPSS 81.44%, 100th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2020-26258

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2020-26258

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 93.68% 81.44% -12.24%
2 2025-11-21 88.36% 93.68% +5.32%
3 2025-11-18 — 88.36% —

Full EPSS history (29 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-26258

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 1.8 4.0 [email protected]
7.7 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.1 4.0 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2020-26258

GitHub Security Advisory for CVE-2020-26258

GHSA-4cch-wxpw-8p28 · Severity: medium · Ecosystem: maven — Server-Side Forgery Request can be activated unmarshalling with XStream

OS Trackers for CVE-2020-26258

vendor priority summary link
debian not yet assigned CVE-2020-26258 not yet assigned priority: Debian including 1 source packages (libxstream-java), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-26258
redhat medium — https://access.redhat.com/security/cve/CVE-2020-26258
suse medium CVE-2020-26258 severity moderate: SUSE including 303 source package names (5.0.0-beta1.2.122:xpp3-1.1.4c-11.2.2, 5.0.0-beta1.2.122:xpp3-minimal-1.1.4c-11.2.2, …), 373 product×package rows across 30 product lines (Container suse/manager/5.0/x86_64/server, Container suse/multi-linux-manager/5.1/x86_64/server, … (30 product lines)): Known Affected 231, Fixed 142. https://www.suse.com/security/cve/CVE-2020-26258/
ubuntu medium CVE-2020-26258 medium priority: Ubuntu including 1 source packages (libxstream-java), 14 status rows across 14 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, trusty, upstream, xenial): not-affected 8, released 6. https://ubuntu.com/security/CVE-2020-26258

Affected software / configurations for CVE-2020-26258

Vendor Product Version Raw CPE
apache struts < 6.0.0 cpe:2.3:a:apache:struts:*:*:*:*:*:*:*:*
xstream xstream < 1.4.15 cpe:2.3:a:xstream:xstream:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

References for CVE-2020-26258

URL Tags
https://github.com/x-stream/xstream/security/advisories/GHSA-4cch-wxpw-8p28 Mitigation Third Party Advisory
https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34@%3Ccommits.struts.apache.org%3E Issue Tracking Mailing List
https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP Mailing List
https://lists.fedoraproject.org/archives/list/[email protected]/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7 Mailing List
https://lists.fedoraproject.org/archives/list/[email protected]/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB Mailing List
https://security.netapp.com/advisory/ntap-20210409-0005 Third Party Advisory
https://www.debian.org/security/2021/dsa-4828 Third Party Advisory
https://x-stream.github.io/CVE-2020-26258.html Exploit Mitigation Third Party Advisory
https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34%40%3Ccommits.struts.apache.org%3E Issue Tracking Mailing List
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/ Mailing List
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/ Mailing List
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/ Mailing List
https://security.netapp.com/advisory/ntap-20210409-0005/ Third Party Advisory
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