CVE-2020-26258
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Server-Side Forgery Request can be activated unmarshalling with XStream
rank 53 = 27 + 19 + 0 + 7 + 0
rank@v1 · this cycle
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.81817 · without this subject the record ranks 26
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 7.7, from NVD · without this subject the record ranks 34
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 53
How much of the world it touches
NVD CPE configurations
7 products in the CPE ranges · without this subject the record ranks 46
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 53
$2.50M = $4.99M incident cost x 0.6121449559255632 exposure x 0.81817 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
XStream is one instance of CWE-918, server-side request forgery (ssrf). The index holds 3592 prior instances of this class, 24 KEV-listed. 3 neighbors share the mechanism; each carries its own record state. taxonomy@v1
Sources disagree here.
Both shown, dated. We don't pick winners. disagreement-rules@v1
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Harm, if it fires from the vector and the weakness
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CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Proof-of-concept published · 2 public repositories, 2021-01-22.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published · 2 public repositories2021-01-22receipt
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
Affected & Fixed Versions as published
Show all 7 published ranges
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
Attack path
What it is stated by the CNA
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. receipt
Read the rest of the CNA's description
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.
NVD's analysis a second authority
- severity
- 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
- weakness
- CWE-918
- affected versions
- xstream < 1.4.15; apache struts < 6.0.0; debian linux 9.0; and 4 more, listed in full below
- also scored by
- [email protected] 6.3 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
The CNA scored it 6.3 and NVD 7.7. Both are shown because both were published; we do not pick one.
check it yourself github.com lists.apache.org lists.debian.org lists.fedoraproject.org lists.fedoraproject.org lists.fedoraproject.org +3 morereceipt
Dated events
Movement the material steps
Show all 31 observations
31 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The pattern, elsewhere
XStream is one instance of CWE-918, server-side request forgery (ssrf). The index holds 3592 prior instances of this class, 24 KEV-listed. 3 neighbors share the mechanism; each carries its own record state. [email protected]
3592 records in this class held. The six above are ranked by exploit maturity, then recency.
Siblings and hubs
Records related to this one
None. No alias set, and nothing in the corpus cites this identifier or shares its product family within 60 days.
Browse the index from here
These are index-wide views, not findings about CVE-2020-26258.
What usually comes next
Everything above needs no account. What is below is work: assembling it, scoping it to your estate, watching it, and handing it to someone else.