CVE-2026-86434

HIGHPre-NVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-07. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source

Also known asEUVD-2026-72392 (ENISA EUVD) · GHSA-jcmh-chhq-rh2x (GitHub Security Advisories)Source: ENISA EUVD

7.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

league/commonmark versions >= 2.0.0 and < 2.8.4 (patched in 2.9.0) contain a denial of service vulnerability in UniqueSlugNormalizer::normalize(), which restarts its numeric-suffix search from 1 on every slug collision, resulting in O(K^2) time complexity for K headings that collapse to the same base slug. The vulnerable path is reached when HeadingPermalinkExtension, FootnoteExtension, or TableOfContentsExtension is registered. An unauthenticated attacker can force many headings onto a single base slug (e.g., via empty ATX headings, identical heading text, or punctuation-only headings) in a small Markdown document, consuming excessive CPU and denying service.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.5% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.5%
EPSS %ILE
44th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-10). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

September 7, 2026

Last Modified

October 8, 2026

Advisory Details (2)

Auto-updated Sep 7, 2026
Patch available. Sources: github.
Web page

commonmark 2.0.0 through 2.8.3 Denial of Service via Slug Collision | Advisories | VulnCheck

https://www.vulncheck.com/advisories/commonmark-2.0.0-through-2.8.3-denial-of-service-via-slug-collision
GitHub advisoryMentions a patch (unverified)

Denial of service via colliding heading slugs · Advisory · thephpleague/commonmark · GitHub

https://github.com/thephpleague/commonmark/security/advisories/GHSA-mh25-x5hq-wrqp

Vendor Advisories for CVE-2026-86434(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(4 across 4 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
php-league-commonmark2.10.0-1 ... 2.9.0-1 (25 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
php-league-commonmark2.10.0-1 ... 2.9.0-1 (13 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
php-league-commonmark2.7.0-1 ... 2.8.3-1 (8 versions)
  • every version up to 2.9.0-1: fixed in 2.9.0-1
—
Packagist(1)
PackageVulnerable rangeFix by version rangeDependents
league/commonmark2.0.0 ... 2.8.3 (43 versions)
  • 2.0.0 up to 2.9.0: fixed in 2.9.0
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 34× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 182 rows on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 82 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 16:57 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  2. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  3. 2026-11-11 16:41 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  4. 2026-11-11 06:33 UTCEchelonGraph re-scored
  5. 2026-11-11 06:33 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  6. 2026-11-10 16:45 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  7. 2026-11-09 16:36 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  8. 2026-11-08 16:41 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  9. 2026-11-07 16:40 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  10. 2026-11-06 16:39 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  11. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  12. 2026-11-04 16:37 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  13. 2026-11-04 01:59 UTCEchelonGraph re-scored
  14. 2026-11-04 01:59 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  15. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  16. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  17. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  18. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  19. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  20. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  21. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  22. 2026-10-27 21:25 UTCEchelonGraph re-scored
  23. 2026-10-27 21:25 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  24. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  25. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
Show 75 more
  1. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  2. 2026-10-25 13:54 UTCEchelonGraph re-scored
  3. 2026-10-24 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  4. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  5. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  6. 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  7. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  8. 2026-10-20 09:55 UTCEchelonGraph re-scored
  9. 2026-10-20 09:55 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  10. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  12. 2026-10-18 03:04 UTCEchelonGraph re-scored
  13. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  14. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  15. 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  16. 2026-10-14 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  17. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  18. 2026-10-13 05:20 UTCEchelonGraph re-scored
  19. 2026-10-13 05:19 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  20. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  21. 2026-10-12 14:51 UTCEchelonGraph re-scored
  22. 2026-10-11 19:17 UTCEchelonGraph re-scored
  23. 2026-10-11 16:33 UTCEchelonGraph re-scored
  24. 2026-10-11 13:51 UTCEchelonGraph re-scored
  25. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  26. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  27. 2026-10-10 10:22 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  28. 2026-10-09 22:45 UTCEchelonGraph re-scored
  29. 2026-10-09 22:45 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  30. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  31. 2026-10-09 04:17 UTCEchelonGraph re-scored
  32. 2026-10-09 04:17 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  33. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  34. 2026-10-08 16:34 UTCEchelonGraph re-scored
  35. 2026-10-08 16:34 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  36. 2026-10-08 15:39 UTCEchelonGraph re-scored
  37. 2026-10-08 15:39 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  38. 2026-10-08 10:18 UTCEchelonGraph re-scored
  39. 2026-10-08 10:18 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  40. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  41. 2026-10-07 22:39 UTCEchelonGraph re-scored
  42. 2026-10-07 22:39 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  43. 2026-10-07 10:46 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  44. 2026-10-06 23:11 UTCEchelonGraph re-scored
  45. 2026-10-06 23:11 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  46. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  47. 2026-10-06 11:37 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  48. 2026-10-06 00:01 UTCEchelonGraph re-scored
  49. 2026-10-06 00:01 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  50. 2026-10-05 17:44 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  51. 2026-10-05 11:38 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  52. 2026-10-05 00:03 UTCEchelonGraph re-scored
  53. 2026-10-05 00:03 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  54. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  55. 2026-10-04 12:28 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  56. 2026-10-04 00:53 UTCEchelonGraph re-scored
  57. 2026-10-04 00:53 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  58. 2026-10-03 13:08 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  59. 2026-10-03 01:32 UTCEchelonGraph re-scored
  60. 2026-10-03 01:32 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  61. 2026-10-02 13:57 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  62. 2026-10-02 02:06 UTCEchelonGraph re-scored
  63. 2026-10-02 02:05 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  64. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  65. 2026-10-01 14:28 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  66. 2026-10-01 02:53 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  67. 2026-09-30 15:19 UTCEchelonGraph re-scored
  68. 2026-09-30 15:19 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  69. 2026-09-30 15:04 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  70. 2026-09-30 02:30 UTCEchelonGraph re-scored
  71. 2026-09-30 02:30 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  72. 2026-09-29 12:48 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  73. 2026-09-29 01:13 UTCEchelonGraph re-scored
  74. 2026-09-29 01:13 UTCGHSA enrichmentGHSA-jcmh-chhq-rh2x · GitHub severity HIGH · GitHub CVSS 7.5
  75. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.5% · 41st percentile

Frequently asked(5)

What is CVE-2026-86434?
CVE-2026-86434 is a high-severity vulnerability; its CVE record was published on September 7, 2026. league/commonmark versions >= 2.0.0 and < 2.8.4 (patched in 2.9.0) contain a denial of service vulnerability in UniqueSlugNormalizer::normalize(), which restarts its numeric-suffix search from 1 on every slug collision, resulting in O(K^2) time complexity for K headings that collapse to the same…
When was CVE-2026-86434 made public?
CVE-2026-86434 was made public on August 3, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on September 7, 2026. EchelonGraph's copy of the record carries a last-modified date of October 8, 2026; the record at its source may have been updated since.
Is CVE-2026-86434 actively exploited?
CVE-2026-86434 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (44th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-86434?
CVE-2026-86434 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-86434?
A fix for CVE-2026-86434 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-86434 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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