CVE-2026-86428
commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
CVE-2026-86428- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
EUVDEUVD-2026-72386
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
EUVD-2026-72386- CVSS 4.0
- 8.7 High
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 - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-8h74-w38m-j62j
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the...
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
GHSA-8h74-w38m-j62j- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
NVD
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
CVE-2026-86428- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-407
- Updated
- 2026-11-02
OSV
commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
CVE-2026-86428- CVSS 4.0
- 8.7 High
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 - Weakness
- CWE-407
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-86428
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
DEBIAN-CVE-2026-86428- CVSS 4.0
- 8.7 High
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 - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-86428
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
- Record
UBUNTU-CVE-2026-86428- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
php-league-commonmarkDebian:12 |
All versions, plus listed versions 2.10.0-12.10.1-12.10.3-12.3.9-12.3.9-1+deb12u1 Show 20 moreShow less2.4.0-12.4.1-12.4.2-12.4.2-22.5.0-12.5.1-12.5.3-12.6.0-12.6.1-12.6.1-22.6.2-12.7.0-12.7.1-12.7.1-22.8.0-12.8.1-12.8.2-12.8.2-22.8.3-12.9.0-1 |
None known |
php-league-commonmarkDebian:13 |
All versions, plus listed versions 2.10.0-12.10.1-12.10.3-12.7.0-12.7.0-1+deb13u1 Show 8 moreShow less2.7.1-12.7.1-22.8.0-12.8.1-12.8.2-12.8.2-22.8.3-12.9.0-1 |
None known |
php-league-commonmarkDebian:14 |
before 2.10.0-1, plus listed versions 2.7.0-12.7.1-12.7.1-22.8.0-12.8.1-1 Show 4 moreShow less2.8.2-12.8.2-22.8.3-12.9.0-1 |
2.10.0-1 |
php-league-commonmarkUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 1.1.2-11.2.0-11.3.0-11.3.1-11.3.1-1ubuntu21.3.1-1ubuntu2+esm1 |
None known |
php-league-commonmarkUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 1.5.7-2build11.6.6-1build11.6.7-11.6.7-1ubuntu0.1~esm1 |
None known |
php-league-commonmarkUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 2.3.9-12.4.1-12.4.2-12.4.2-22.4.2-2ubuntu0.1~esm1 |
None known |
php-league-commonmarkUbuntu:26.04:LTS |
All versions, plus listed versions 2.7.0-12.7.1-22.8.0-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-86428 is a high vulnerability (CVSS 8.7) in Thephpleague Commonmark, published September 7, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.49%, the 42nd percentile. Fixed in php-league-commonmark 2.10.0-1.
References
github.com/thephpleague/commonmark/security/advisories/GHSA-8rr7-cvq3-gmfh
vulncheck.com/advisories/commonmark-1.5.0-before-2.10.0-denial-of-service-via-attributes
nvd.nist.gov/vuln/detail/CVE-2026-86428
security-tracker.debian.org/tracker/CVE-2026-86428
ubuntu.com/security/CVE-2026-86428
cve.org/CVERecord?id=CVE-2026-86428