{"id":"CVE-2020-26258","url":"https://www.cyber-defence.io/tools/cve/CVE-2020-26258","generatedAt":"2026-10-27T23:38:47.195Z","title":"In XStream before version 1.4.15, a Server-Side Forgery Request vulnerability can be activated when unmarshalling.","description":"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":"2020-12-16T01:15:12.000Z","lastModified":"2026-10-07T19:17:18.000Z","status":"Analyzed","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":7.7,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N"},"cwe":["CWE-918"],"affected":["apache/struts","xstream/xstream","debian/debian linux","fedoraproject/fedora"],"epss":{"score":0.81817,"percentile":0.99643,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 81.8%, higher than 100% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"https://github.com/x-stream/xstream/security/advisories/GHSA-4cch-wxpw-8p28","tags":["Mitigation","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34@%3Ccommits.struts.apache.org%3E","tags":["Issue Tracking","Mailing List"],"source":"security-advisories@github.com"},{"url":"https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html","tags":["Mailing List","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP","tags":["Mailing List"],"source":"security-advisories@github.com"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7","tags":["Mailing List"],"source":"security-advisories@github.com"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB","tags":["Mailing List"],"source":"security-advisories@github.com"},{"url":"https://security.netapp.com/advisory/ntap-20210409-0005","tags":["Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://www.debian.org/security/2021/dsa-4828","tags":["Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://x-stream.github.io/CVE-2020-26258.html","tags":["Exploit","Mitigation","Third Party Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/x-stream/xstream/security/advisories/GHSA-4cch-wxpw-8p28","tags":["Mitigation","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.apache.org/thread.html/r97993e3d78e1f5389b7b172ba9f308440830ce5f051ee62714a0aa34%40%3Ccommits.struts.apache.org%3E","tags":["Issue Tracking","Mailing List"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2020/12/msg00042.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/22KVR6B5IZP3BGQ3HPWIO2FWWCKT3DHP/","tags":["Mailing List"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PVPHZA7VW2RRSDCOIPP2W6O5ND254TU7/","tags":["Mailing List"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGXIU3YDPG6OGTDHMBLAFN7BPBERXREB/","tags":["Mailing List"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.netapp.com/advisory/ntap-20210409-0005/","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.debian.org/security/2021/dsa-4828","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://x-stream.github.io/CVE-2020-26258.html","tags":["Exploit","Mitigation","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2020-26258","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}