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CVE-2021-33455

20
FAUCET Score

CVE-2021-33455 describes a NULL pointer dereference vulnerability in yasm version 1.3.0, specifically within the do_directive() function in modules/preprocs/nasm/nasm-pp.c. This flaw carries a CVSS score of 5.5 (Medium), indicating a local attack vector with low complexity, requiring user interaction, and primarily leading to high availability impact. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
1.3.0CPE matchmatch criteria
cpe:2.3:a:tortall:yasm:1.3.0:*:*:*:*:*:*:*

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
0.32%
Probability of exploitation in next 30 days
EPSS Percentile
24.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0032 is in the 30th percentile among its peer group of 5,758 CVEs.

Social Chatter

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

Patch Available

Vendor Patches (4)

microsoftpatch availablevia msrc
Product: 17890-16820Fixed in: 1.3.0-14
microsoftpatch availablevia msrc
Product: 18874-16823Fixed in: 1.3.0-16
microsoftpatch availablevia msrc
Product: cm1 yasm 1.3.0-14 on CBL Mariner 1.0Fixed in: 1.3.0-14
microsoftpatch availablevia msrc
Product: cbl2 yasm 1.3.0-16 on CBL Mariner 2.0Fixed in: 1.3.0-16

Vendor Advisories (1)

microsoft2022-Jul/CVE-2021-33455Moderate

An issue was discovered in yasm version 1.3.0. There is a NULL pointer dereference in do_directive() in modules/preprocs/nasm/nasm-pp.c.

Jul 12, 2022

References

gist.github.com / Clingto/bb632c0c463f4b2c97e4f65f751c5e6d
Third Party Advisory
github.com / yasm/yasm/issues/169
ExploitIssue TrackingThird Party Advisory