rdiscount has an Out-of-bounds Read

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-35201: 0.29% estimated exploitation activity in the next 30 days; percentile 21.13 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A signed length truncation bug causes an out-of-bounds read in the default Markdown parse path. Inputs larger than INTMAX are truncated to a signed int before entering the native parser, allowing the parser to read past the end of the supplied buffer and crash the process Details In both public entry points: - ext/rdiscount.c:97 - ext/rdiscount.c:136 RSTRINGLEN(text) is passed directly into mkdstring(): mkdstring() accepts int len: - ext/mkdio.c:174 The parser stores the remaining input length in a signed int: - ext/markdown.h:205 The read loop stops only when size == 0: - ext/mkdio.c:161 If the Ruby string length exceeds INTMAX, the value can truncate to a negative int. In that state, the parser continues incrementing data and reading past the end of the original Ruby string, causing an out-of-bounds read and native crash. Affected APIs: - RDiscount.new(input).tohtml - RDiscount.new(input).toccontent PoC Crash via tohtml: result: - built=2200000000 - Ruby terminates with…

Published by the source

6 Apr 2026, 17:53 UTC

Last modified by the source

13 May 2026, 16:20 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6r34-94wq-jhrc

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-35201

Advisory: rdiscount has an Out-of-bounds Read
IDs: CVE-2026-35201, GHSA-6r34-94wq-jhrc
Record: https://patchnext.com/advisories/cve-2026-35201 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: rdiscount 2.2.7.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems rdiscount: affected >= 1.3.1.1, < 2.2.7.4; fixed in 2.2.7.4

## Suggested inspection (read-only)
- RubyGems rdiscount: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on rdiscount.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6r34-94wq-jhrc (GitHub-reviewed advisory GHSA-6r34-94wq-jhrc lists affected ranges: RubyGems rdiscount >=1.3.1.1 <2.2.7.4)

Commands are suggestions: review each one before running it.