CVE-2023-4863: in the CISA KEV catalogue

Google Chromium WebP Heap-Based Buffer Overflow Vulnerability. CISA added CVE-2023-4863 to the Known Exploited Vulnerabilities catalogue on 2023-09-13 with a default due date of 2023-10-04. Known ransomware campaign use: Unknown. Forensic triage flag: No.

Google Chromium WebP contains a heap-based buffer overflow vulnerability that allows a remote attacker to perform an out-of-bounds memory write via a crafted HTML page. This vulnerability can affect applications that use the WebP Codec. (CISA description)

Vendor / product: Google Chromium WebP
CWE: CWE-787
CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
EPSS: 100%, percentile 99 (scored 2026-11-03)

EPSS puts nearly every time in 100 odds (100%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 99% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.

Vendor and reference links (from CISA)

Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.

Data dates. CISA KEV catalogue version 2026.11.03, released 2026-11-03, 1,767 entries (checked 2026-11-03). EPSS model v2026.06.15, scored 2026-11-03, 399,388 CVEs. Sources: CISA and FIRST (EPSS by FIRST; scores generated by Empirical Security). Copied to our own database and refreshed automatically; if a refresh fails, the previous copy keeps serving with its own date.

Frequently asked questions

Is CVE-2023-4863 in the CISA KEV catalogue?

Yes. CISA added CVE-2023-4863 (Google Chromium WebP Heap-Based Buffer Overflow Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2023-09-13. CISA's default due date for it is 2023-10-04.

Is CVE-2023-4863 used in ransomware attacks?

CISA marks known ransomware campaign use as Unknown for CVE-2023-4863. That means CISA lacks confirmation, not that ransomware groups do not use it.

What should I do about CVE-2023-4863?

CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Sources

CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
NVD record for CVE-2023-4863