CVE-2026-66731

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

• ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
• AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.78% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 55.7% of scored records. A rank, not a probability.

NVD base score

8.7 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Deferred. NVD last modified this record on 2026-10-24.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-07-27 16:57Z3 MO AGO

Last updated

2026-07-31 18:20Z2 MO AGO

Reserved

2026-07-27

Assigning CNA

VulnCheck

Record state

PUBLISHED

Severity

High (CVSS 8.7)

CNA CVSS vector

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

Weaknesses

• CWE-125Out-of-bounds ReadBase

Data version

5.2

Document digest

481ee54f1b09b8794fd1cd47379957a6a740ac123b3187c07c19db885ce6c184

• tpaidakis.comResearcher Bloghttps://tpaidakis.com/writeups/facilio-parser-dos/technical-descriptionexploit
• github.comResearcher Disclosurehttps://github.com/theopaid/Negative-Chunk-Size-Parsing-Causes-Memory-Corruption-in-facil.io-leading-to-Server-Crashtechnical-descriptionexploit
• www.vulncheck.comhttps://www.vulncheck.com/advisories/facil-io-http-chunked-transfer-encoding-parser-crash-dosthird-party-advisory