CVE-2020-21686
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm...
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
CVE-2020-21686- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-562
- Updated
- 2026-11-02
CVE List No score
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
CVE-2020-21686- Weakness
- CWE-562
- Updated
- 2026-11-02
EUVDEUVD-2020-14454 No score
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
EUVD-2020-14454- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-f5w2-2h32-hmg6
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm...
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
GHSA-f5w2-2h32-hmg6- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-562
- Updated
- 2026-11-02
OSV
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
CVE-2020-21686- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2020-21686
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
DEBIAN-CVE-2020-21686- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVJLSEC-2026-201
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
JLSEC-2026-201- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVOESA-2024-1814
nasm security update
NASM is the Netwide Assembler, a free portable assembler for the Intel 80x86 microprocessor series, using primarily the traditional Intel instruction mnemonics and syntax. It also provides tools in RDOFF binary format, includes linker, library manager, loader, and information dump.
Security Fix(es):
Buffer Overflow vulnerability in hash_findi function in hashtbl.c in nasm 2.15rc0 allows remote attackers to cause a denial of service via crafted asm file.(CVE-2020-21685)
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.(CVE-2020-21686)
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.(CVE-2020-21687)
- Record
OESA-2024-1814- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2020-21686
A stack-use-after-scope issue discovered in expand_mmac_params function in preproc.c in nasm before 2.15.04 allows remote attackers to cause a denial of service via crafted asm file.
- Record
UBUNTU-CVE-2020-21686- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
nasmDebian:12 |
before 2.15.04-1 | 2.15.04-1 |
nasmDebian:13 |
before 2.15.04-1 | 2.15.04-1 |
nasmDebian:14 |
before 2.15.04-1 | 2.15.04-1 |
NASM_jllJulia |
before 2.16.1+0 | 2.16.1+0 |
nasmopenEuler:20.03-LTS-SP4 From an advisory covering 3 CVEs |
before 2.15.05-1.oe2003sp4 | 2.15.05-1.oe2003sp4 |
nasmUbuntu:16.04:LTS |
All versions, plus listed versions 2.11.06-1really2.11.05-12.11.08-12.11.08-1ubuntu0.1 |
None known |
nasmUbuntu:18.04:LTS |
All versions, plus listed versions 2.13.01-22.13.02-0.1 |
None known |
nasmUbuntu:20.04:LTS |
All versions, plus listed versions 2.14.02-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-21686 is a medium vulnerability (CVSS 5.5) in Nasm Netwide Assembler, published August 22, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.44%, the 38th percentile. Fixed in nasm 2.15.04-1.
References
bugzilla.nasm.us/show_bug.cgi?id=3392643
nvd.nist.gov/vuln/detail/CVE-2020-21686
github.com/advisories/GHSA-f5w2-2h32-hmg6
security-tracker.debian.org/tracker/CVE-2020-21686
openeuler.org/zh/security/security-bulletins/detail?id=openEuler-SA-2024-1814
ubuntu.com/security/CVE-2020-21686
cve.org/CVERecord?id=CVE-2020-21686