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Fencer Intel
medium 5.3

CVE-2025-6493 json

CodeMirror Markdown Mode markdown.js redos

published last yr. modified 4mo ago also EUVD-2025-28740

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

A weakness has been identified in CodeMirror up to 5.65.20. Affected is an unknown function of the file mode/markdown/markdown.js of the component Markdown Mode. This manipulation causes inefficient regular expression complexity. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be exploited. Upgrading to version 6.0 is able to address this issue. You should upgrade the affected component. Not all code samples mentioned in the GitHub issue can be found. The repository mentions, that "CodeMirror 6 exists, and is [...] much more actively maintained."

Patch / fix

  • n/a CodeMirror 6.0

Is CVE-2025-6493 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2025-6493 updated cvss 5.3

codemirror: CodeMirror Markdown Regex Complexity Vulnerability

  • Red Hat OpenShift Serverless openshift-serverless-1/kn-backstage-plugins-eventmesh-rhel8 Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9, rhdh/rhdh-rhel9-operator Red Hat Enterprise Linux 7 firefox, thunderbird Red Hat Enterprise Linux 8 mozjs60 Red Hat Enterprise Linux 9 gjs, polkit, polkit-libs Red Hat Enterprise Linux 10 gjs
    +6 more products
    Red Hat Fuse 7 io.hawt-project, io.hawt-hawtio-online, io.syndesis-syndesis-parent Red Hat JBoss Enterprise Application Platform 7 io.hawt-project Red Hat JBoss Enterprise Application Platform 8 io.hawt-project Red Hat JBoss Enterprise Application Platform Expansion Pack io.hawt-project Red Hat OpenShift Container Platform 4 openshift4/ose-monitoring-plugin-rhel8, openshift4/ose-monitoring-plugin-rhel9 Red Hat OpenShift Dev Spaces devspaces/dashboard-rhel8, devspaces/dashboard-rhel9
    not affected: vulnerable code 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
last yr.

Exploit prediction

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/codemirror/codemirror5/issues/7128 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
CNA 3.0 5.3 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
CNA 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C
CNA 4.0 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/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
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CNA 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • n/a CodeMirror

Classification

Weakness
  • CWE-1333 Inefficient Regular Expression Complexity
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Intel 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.