{"cve":"CVE-2026-48788","nvd":{"published":"2026-06-17T13:20:43.490","modified":"2026-10-25T23:10:00.167","status":"Deferred","description":"Remark42 is a self-hosted comment engine for blogs, articles, or any other place where readers can add comments. Versions 1.6.0 through 1.15.0 contain a Cross-Site Scripting (XSS) vulnerability exploitable through content-type spoofing. The Remark42 image proxy fetches an arbitrary remote URL and re-serves the response from Remark42's own origin. During the download phase, the proxy determines whether the resource is an image by inspecting only the Content-Type header advertised by the remote server, never examining the actual bytes; during the serving phase, it instead derives the response Content-Type by sniffing those bytes with http.DetectContentType. An attacker can exploit this inconsistency by hosting a URL that advertises Content-Type: image/png while returning an HTML/JavaScript body: the download check accepts it as an image, the serving path sniffs the body and emits Content-Type: text/html, and the browser renders the attacker-controlled HTML/JavaScript as a document within Remark42's origin. Exploitation requires no Remark42 account on the target instance; the attacker only needs to host the malicious upstream URL and deliver the proxy link to a victim by any means, such as email, direct message, or a link on another website. This issue has been fixed in version 1.16.0.","cvss_v4":null,"cvss_v3":{"version":"3.0","vector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N","score":8.2},"cwes":["CWE-79","CWE-436"],"references":["https://github.com/umputun/remark42/commit/78d6de6bce1e961f023969da3ec8a00dd80c9ae8","https://github.com/umputun/remark42/releases/tag/v1.16.0","https://github.com/umputun/remark42/security/advisories/GHSA-4c8j-mgm4-qqvp","https://github.com/umputun/remark42/security/advisories/GHSA-4c8j-mgm4-qqvp"],"products":[],"source":"nvd","synced_at":"2026-10-25T23:44:33.281319194+00:00"},"epss":{"cve":"CVE-2026-48788","score":0.00247,"percentile":0.15853,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-4c8j-mgm4-qqvp","url":"https://osv.dev/vulnerability/GHSA-4c8j-mgm4-qqvp","summary":"Remark42: Cross-Site Scripting (XSS) on /api/v1/img via content-type spoofing","modified":"2026-07-07T16:11:13.898247373Z","packages":[{"ecosystem":"Go","name":"github.com/umputun/remark42","purl":"pkg:golang/github.com/umputun/remark42","ranges":[">=1.6.0 <1.16.0"],"fixed":["1.16.0"]}]},{"id":"GO-2026-5804","url":"https://osv.dev/vulnerability/GO-2026-5804","summary":"Remark42: Cross-Site Scripting (XSS) on /api/v1/img via content-type spoofing in github.com/umputun/remark42","modified":"2026-07-07T16:01:34.714025374Z","packages":[{"ecosystem":"Go","name":"github.com/umputun/remark42","purl":"pkg:golang/github.com/umputun/remark42","ranges":[">=1.6.0 <1.16.0"],"fixed":["1.16.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}