How severe is CVE-2026-86435?

CVE-2026-86435 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-86435 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (40th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-86435?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-86435 published?

CVE-2026-86435 was published on 2026-09-07 and last updated on 2026-09-09.

CVE-2026-86435

CVE-2026-86435 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-407.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.7
EPSS exploit prediction: 0% (40th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-407
Published: 2026-09-07
Last modified: 2026-09-09

Description

commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Footnote extension that fails to deduplicate footnote definitions. Attackers can craft documents with duplicate footnote definitions and references to create quadratic output expansion, consuming excessive memory and CPU to exhaust server resources.

Frequently asked questions

What is CVE-2026-86435?: commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Footnote extension that fails to deduplicate footnote definitions. Attackers can craft documents with duplicate footnote definitions and references to create quadratic output expansion, consuming excessive memory and CPU to exhaust server resources.
How severe is CVE-2026-86435?: CVE-2026-86435 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-86435 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (40th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-86435?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-86435 published?: CVE-2026-86435 was published on 2026-09-07 and last updated on 2026-09-09.

References

Other CWE-407 vulnerabilities

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CVE-2026-83613 — High (CVSS 8.7): xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to…
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CVE-2026-65623 — High (CVSS 8.7): Inefficient Algorithmic Complexity vulnerability in mtrudel bandit allows unauthenticated remote denial of service via…

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