What is CVE-2020-18780?

CVE-2020-18780 is a medium-severity vulnerability in Nasm Netwide Assembler, classified under Use After Free. CVSS score: 5.5/10. Published 2023-08-22.

How severe is CVE-2020-18780?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Is CVE-2020-18780 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Use After Free in Nasm Netwide Assembler

CVE-2020-18780

A Use After Free vulnerability in function new_Token in asm/preproc.c in nasm 2.14.02 allows attackers to cause a denial of service via crafted nasm command.

Vulnerability class: Use-After-Free

Published 2023-08-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.003 (19.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 19.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Nasm Netwide Assembler — versions 2.14.02

Weakness classification (CWE)

CWE-416 — Use After Free

Public proof-of-concept exploits

ARPSyndicate/cve-scores

References

bugzilla.nasm.us/show_bug.cgi (Exploit, Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2020-18780?: CVE-2020-18780 is a medium-severity vulnerability in Nasm Netwide Assembler, classified under Use After Free. CVSS score: 5.5/10. Published 2023-08-22.
How severe is CVE-2020-18780?: Medium severity. CVSS v3 base score is 5.5 out of 10.
Is CVE-2020-18780 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.