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Public proof of concept

CVE-2026-88753

markdown2: markdown2: Denial of Service via crafted Markdown document

A public proof of concept exists; no exploitation attested.

  • Published2026-10-15
  • WeaknessCWE-400

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2026-10-1516:18CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-88753?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-88753?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • CVE-2026-88753 Red Hat Product Security1 known affected

    markdown2: markdown2: Denial of Service via crafted Markdown document

    openshift4/ose-olm-catalogd-rhel9 as a component of Red Hat OpenShift Container Platform 4

Full record on NVD

Fix

  1. Workaround from the vendor Red Hat Product Security CVE-2026-88753 · 1 productThe vulnerable code path is only reached when markdown2 is used with the opt-in `metadata` extra. Where feasible, applications that render untrusted Markdown should avoid enabling the `metadata` extra; upstream analysis confirms that the same input is processed in linear time when that extra is dis…
  2. No fix available, says the vendor Red Hat Product Security CVE-2026-88753 · 1 productFix deferred

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-10-15
Last Modified
2026-10-20
NVD status
Deferred

Frequently asked questions

What is CVE-2026-88753?

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.

Is CVE-2026-88753 actively exploited?

A proof-of-concept exploit exists for CVE-2026-88753, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-88753?

CVE-2026-88753 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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