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CVE-2020-21686

16
FAUCET Score

CVE-2020-21686 is a stack-use-after-scope vulnerability found in the expand_mmac_params function within preproc.c of NASM (Netwide Assembler) versions prior to 2.15.04. This flaw allows a remote attacker to trigger a denial of service by providing a specially crafted assembly file. Rated Medium with a CVSS score of 5.5, the vulnerability requires user interaction (UI:R) and local access (AV:L) to exploit, leading to high availability impact (A:H). There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.15.04CPE matchmatch criteria
cpe:2.3:a:nasm:netwide_assembler:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.5MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.38%
Probability of exploitation in next 30 days
EPSS Percentile
30.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0038 is in the 37th percentile among its peer group of 5,758 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

redhatCVE-2020-21686Low

nasm: stack-use-after-scope in expand_mmac_params() in preproc.c

Jan 6, 2020

References

bugzilla.nasm.us / show_bug.cgi
ExploitIssue TrackingVendor Advisory