# CVE-2026-126771: OpsTree REMS through 1.0.0 Stored XSS via Attachment Upload and Preview

Status: published. Published: 2026-11-11. Updated: 2026-11-11.

OpsTree REMS through 1.0.0 contains a stored cross-site scripting vulnerability that allows authenticated attackers to inject scripts by uploading attachments with spoofed text/html Content-Type. Attackers can upload HTML files named like test.html.pdf that render in the REMS origin via Preview, executing JavaScript in victims' browsers.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- OpsTree Solutions / REMS: ≥ 0; ≤ 1.0.0 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-79

## Exploit evidence

- exploit: https://gist.github.com/neelkotnis/ddf75e2cb7192180e6c9618d27d1e99b (CNA: VulnCheck)

## References

- https://gist.github.com/neelkotnis/ddf75e2cb7192180e6c9618d27d1e99b (CNA: VulnCheck; technical-description, exploit)

- https://opstree.com/rems-ai-powered-observability/ (CNA: VulnCheck; product)

- https://www.vulncheck.com/advisories/opstree-rems-through-1.0.0-stored-xss-via-attachment-upload-and-preview (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-126771; retrieved 2026-11-11; source updated 2026-11-11

Revision: 4fa0ab8b93e8cc7e6fddf6e41c461a683e102842fb04a9f7851416a8d077e34d

Canonical: https://y2.dev/cve/CVE-2026-126771

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.