CVE-2021-33455

Exp

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.

Published: 2022-07-26 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33455 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.14%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-33455

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-33455

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.05% 0.14% +0.09%
2 2025-11-18 0.14% 0.05% -0.09%
3 2025-07-27 — 0.14% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33455

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]

Weakness enumeration for CVE-2021-33455

OS Trackers for CVE-2021-33455

vendor priority summary link
alpine medium CVE-2021-33455: 1 source package rows (yasm); 7 state rows across 7 repos (3.17-main, 3.18-main, 3.19-community, 3.20-community, 3.22-community, 3.23-community, edge-community); fixed 0, open 7. https://security.alpinelinux.org/vuln/CVE-2021-33455
debian unimportant CVE-2021-33455 unimportant priority: Debian including 1 source packages (yasm), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 5. https://security-tracker.debian.org/tracker/CVE-2021-33455
suse low CVE-2021-33455 severity low: SUSE including 2 source package names (yasm, yasm-devel), 19 product×package rows across 10 product lines (SUSE CaaS Platform 4.0, SUSE Enterprise Storage 7, … (10 product lines)): Will Not Fix 19. https://www.suse.com/security/cve/CVE-2021-33455/
ubuntu medium CVE-2021-33455 medium priority: Ubuntu including 1 source packages (yasm), 13 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): needs-triage 7, ignored 6. https://ubuntu.com/security/CVE-2021-33455

Affected software / configurations for CVE-2021-33455

Vendor Product Version Raw CPE
tortall yasm 1.3.0 cpe:2.3:a:tortall:yasm:1.3.0:*:*:*:*:*:*:*

References for CVE-2021-33455

URL Tags
https://gist.github.com/Clingto/bb632c0c463f4b2c97e4f65f751c5e6d Third Party Advisory
https://github.com/yasm/yasm/issues/169 Exploit Issue Tracking Third Party Advisory
cvelogic Threat Intelligence