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Fencer Vulns
high 7.5

CVE-2019-25781 json

Python-Markdown 3.0 through 3.11.2 Denial of Service via Link Bracket Parsing

published 2026-10-29 10 d ago modified 2026-11-03 5 d ago also EUVD-2019-20211

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

Python-Markdown 3.0 through 3.11.2 contains an algorithmic complexity vulnerability in inline link parsing that allows remote attackers to exhaust CPU through unmatched brackets. Attackers can submit short Markdown containing repeated [ or ![ characters, forcing LinkInlineProcessor.getText() and getLink() into quadratic scans that keep workers busy for minutes.

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-25781 updated cvss 7.5

markdown: python-markdown: Denial of Service via inefficient inline link parsing

  • Red Hat AI Inference Server rhaii/vllm-cpu-rhel9, rhaii/vllm-cuda-rhel9, rhaii/vllm-gaudi-rhel9, rhaii-fast/vllm-cpu-rhel9, rhaii-fast/vllm-cuda-rhel9, rhaii-fast/vllm-gaudi-rhel9
    affected: no fix available
  • Red Hat Ansible Automation Platform 2 python-markdown 3.3.6-3.el9pc, python3.11-markdown 3.5.2-1.el9ap, python3.12-markdown 3.5.2-2.el9ap, automation-controller 4.5.37-1.el8ap, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, +4 more
    affected: no fix available “Fix deferred”
  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Enterprise Linux 8 python3-markdown Red Hat Enterprise Linux 9 python3-markdown, python-markdown 3.3.6-3.el9pc Red Hat Enterprise Linux 10 python-markdown 3.3.6-3.el9pc Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9 Red Hat OpenShift AI (RHOAI) rhoai/odh-automl-rhel9, rhoai/odh-built-in-detector-rhel9, rhoai/odh-th-torch-cpu-py312-rhel9, rhoai/odh-th-torch-cuda-py312-rhel9, rhoai/odh-th-torch-rocm-py312-rhel9, rhoai/odh-kserve-autogluon-server-rhel9, +24 more
    +4 more products
    Red Hat OpenShift Container Platform 4 openshift4/ose-olm-catalogd-rhel9 Red Hat Satellite 6 python3-markdown, python-markdown 3.3.6-3.el9pc, python3.12-markdown 3.5.2-2.el9ap, satellite/iop-advisor-backend-rhel9 Red Hat Trusted Artifact Signer rhtas/rh-sigstore-a2a-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/bootc-automation-portal-rhel9
    affected: no fix available
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-th06-cpu-torch291-py312-rhel9, rhoai/odh-kserve-storage-initializer-rhel9, rhoai/odh-th06-cuda130-torch291-py312-rhel9
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
5 d ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/Python-Markdown/markdown/issues/1654 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • Python-Markdown Markdown

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.