# CVE-2026-77088 — EmilStenstrom justhtml

> As of 2026-08-23, CVE-2026-77088 is a MEDIUM-severity vulnerability in EmilStenstrom justhtml, CVSS v3.1 6.1. No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-77088 as of 2026-08-23; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-23

## What is CVE-2026-77088?

justhtml versions 0.9.0 through 1.21.0 contain a cross-site scripting vulnerability in to_markdown() where inline code spans fail to account for blank lines as block boundaries. Attackers can inject blank lines into code or pre element text to break the inline span, causing sanitized HTML to be emitted unescaped and re-parsed as live Markdown by compliant renderers.

The record classifies CVE-2026-77088 under weakness class [CWE-79](https://intel.threadlinqs.com/cwe/CWE-79). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 43 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 6.1 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **CVSS v4.0 base score:** 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.1/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-23

## Is CVE-2026-77088 being exploited?

It currently carries a trending score of 30 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [EmilStenstrom](https://intel.threadlinqs.com/vendors/emilstenstrom): justhtml

## How to fix CVE-2026-77088

No vendor patch reference has been recorded for CVE-2026-77088 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-77088

No threat campaign in the Threadlinqs corpus currently references CVE-2026-77088, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org. Last verified by Threadlinqs on 2026-08-24.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-jf6w-2mvx-633j)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/justhtml-through-cross-site-scripting-via-code-span)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-77088
Full detection coverage and IOCs for threats exploiting CVE-2026-77088 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp