Regex denial of service in markdown2 via crafted Markdown
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Deferred Red Hat: fix deferred
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-400.
Summary
markdown2 through v2.5.5 contains a regular expression denial of service flaw in its extract_metadata() function. A regex in this function consumes excessive processing time on crafted input (CWE-400, uncontrolled resource consumption). A remote attacker with no privileges and no user interaction can cause a denial of service by supplying a crafted Markdown document.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
Description from the CNA
A Regular-Expression Denial of Service (ReDoS) in the Markdown2. extract_metadata() function (lib/markdown2.py) of trentm markdown2 through v2.5.5 allows attackers to cause a Denial of Service (DoS) via a crafted Markdown document.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
Remediation
The sources list no fixed version for markdown2. Red Hat lists Red Hat OpenShift Container Platform 4 as affected, with no fix available.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-16 Threatist record created from CVE-2026-88753
- 2026-10-16 Affected versions changed · Red Hat
- 2026-10-16 CVSS score added · Red Hat
- 2026-10-20 Alias added: GHSA-vv85-hg53-g6g2
- 2026-10-20 CVSS score added · CISA ADP
- 2026-10-20 Weakness changed · CISA ADP
- 2026-10-20 CISA SSVC decision points changed
- 2026-10-20 Priority changed: LOW → HIGH
References
Sources
- CVE-2026-88753 · CVE Program
- CVE-2026-88753 · NVD
- FIRST EPSS
- GHSA-vv85-hg53-g6g2 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-88753 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences