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Fencer Intel
medium 5.5

CVE-2020-21687 json

Buffer Overflow vulnerability in scan function in stdscan.c in nasm 2.15rc0 allows remote attackers to cause a denial of service via crafte…

published 3y ago modified 4mo ago also EUVD-2020-14455

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

Buffer Overflow vulnerability in scan function in stdscan.c in nasm 2.15rc0 allows remote attackers to cause a denial of service via crafted asm file.

Patch / fix

  • nasm Debian 14, Debian 13, Debian 12 2.15.04-1

debian advisories DEBIAN-CVE-2020-21687

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-21687 updated cvss 5.5

nasm: stack-based buffer overflow in stdscan() in stdscan.c

  • Red Hat Enterprise Linux 6 nasm, nasm-rdoff Red Hat Enterprise Linux 7 nasm, nasm-rdoff
    affected: no fix planned “Out of support scope”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
2y ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • bugzilla.nasm.us https://bugzilla.nasm.us/show_bug.cgi?id=3392645 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.