{"id":"EUVD-2026-37511","enisaUuid":"f34a318e-5e7b-3a6e-926c-e05ab93624af","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\u0027s 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\u0027s 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.","datePublished":"Jun 16, 2026, 10:29:38 PM","dateUpdated":"Jun 17, 2026, 1:20:11 PM","baseScore":8.2,"baseScoreVersion":"3.0","baseScoreVector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N","references":"https://github.com/umputun/remark42/security/advisories/GHSA-4c8j-mgm4-qqvp\nhttps://github.com/umputun/remark42/commit/78d6de6bce1e961f023969da3ec8a00dd80c9ae8\nhttps://github.com/umputun/remark42/releases/tag/v1.16.0\n","aliases":"CVE-2026-48788\nGHSA-4c8j-mgm4-qqvp\n","assigner":"GitHub_M","epss":0.31,"enisaIdProduct":[{"id":"419dd47c-632d-3635-a360-b05312711d21","product":{"name":"remark42","vendor":{"name":"umputun"}},"product_version":"1.6.0, \u003c 1.16.0"}],"enisaIdVendor":[{"id":"3bdca08b-5ca0-3a7b-8389-179e8c302d65","vendor":{"name":"umputun"}}],"enisaIdVulnerability":[{"id":"26b5fd0d-4433-390b-9a28-fcedb47ec0dc","vulnerability":{"id":"CVE-2026-48788","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\u0027s 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\u0027s 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.","datePublished":"Jun 16, 2026, 10:29:38 PM","dateUpdated":"Jun 17, 2026, 1:20:11 PM","status":"PUBLISHED","baseScore":8.2,"baseScoreVersion":"3.0","baseScoreVector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N","references":"https://github.com/umputun/remark42/security/advisories/GHSA-4c8j-mgm4-qqvp\nhttps://github.com/umputun/remark42/commit/78d6de6bce1e961f023969da3ec8a00dd80c9ae8\nhttps://github.com/umputun/remark42/releases/tag/v1.16.0\n","enisa_id":"EUVD-2026-37511\n","assigner":"GitHub_M","epss":0.31,"dataProcessed":"Nov 7, 2026, 7:22:47 AM","vulnerabilityProduct":[{"id":"d283bc6c-8242-37fb-9119-92c45dad64c2","product":{"name":"remark42","vendor":{"name":"umputun"}},"product_version":"1.6.0, \u003c 1.16.0"}],"vulnerabilityVendor":[{"id":"507dbbdf-9a14-3e9c-8aa6-e00436dded0e","vendor":{"name":"umputun"}}]}},{"id":"9ff67143-7204-341f-9372-916e907016b4","vulnerability":{"id":"GHSA-4c8j-mgm4-qqvp","description":"Remark42: Cross-Site Scripting (XSS) on /api/v1/img via content-type spoofing","datePublished":"Jun 26, 2026, 7:26:43 PM","dateUpdated":"Jun 26, 2026, 7:26:44 PM","baseScore":0.0,"references":"https://github.com/umputun/remark42/security/advisories/GHSA-4c8j-mgm4-qqvp\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-48788\nhttps://github.com/umputun/remark42/commit/78d6de6bce1e961f023969da3ec8a00dd80c9ae8\nhttps://github.com/umputun/remark42\nhttps://github.com/umputun/remark42/releases/tag/v1.16.0\n","enisa_id":"EUVD-2026-37511\n","aliases":"CVE-2026-48788\nGHSA-4c8j-mgm4-qqvp\n","epss":0.0,"dataProcessed":"Nov 1, 2026, 2:01:46 AM","vulnerabilityProduct":[],"vulnerabilityVendor":[]}}],"enisaIdAdvisory":[]}