CVE-2023-49555: An issue in YASM 1.3.0.86.g9def allows a remote attacker to cause a denial of service via the expand_smacro fu

Routine

MEDIUM 5.5DOWNGRADE

CVE-2023-49555 is a medium-severity flaw (CVSS 5.5) affecting yasm. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue in YASM 1.3.0.86.g9def allows a remote attacker to cause a denial of service via the expand_smacro function in the modules/preprocs/nasm/nasm-pp.c component.

Why this priority

Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 68%)
CISA exploited list	No
Weakness	CWE-400
Published	2024-01-03
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: yasm project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-01-03 00:15 UTCPublished CVE record published
2026-06-17 06:36 UTCUpdated Record last modified

yasm project yasm DOWNGRADE

Affected: 1.3.0.86.g9def

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.3.0.86.g9def

1. Check installed version

apt-cache policy yasm || rpm -q yasm || yasm --version

2. No fixed release: DOWNGRADE to a release before 1.3.0.86.g9def (Debian / Ubuntu)

apt-cache madison yasm sudo apt install yasm=<VERSION_BEFORE_1.3.0.86.g9def> sudo apt-mark hold yasm

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list yasm sudo dnf downgrade yasm-<VERSION_BEFORE_1.3.0.86.g9def> sudo dnf versionlock add yasm

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2023-49555?

yasm: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-49555 being exploited?

CVE-2023-49555 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2023-49555 affect?

CVE-2023-49555 affects yasm. Severity is medium (CVSS 5.5). An issue in YASM 1.3.0.86.g9def allows a remote attacker to cause a denial of service via the expand_smacro function in the modules/preprocs/nasm/nasm-pp.c component.

How urgent is CVE-2023-49555?

Priority 32/100. Public exploit reference

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CVE-2023-49558 MEDIUM 5.5 DOWNGRADE An issue in YASM 1.3.0.86.g9def allows a remote attacker to cause a denial of service via the expand_mmac_para
CVE-2023-49557 MEDIUM 5.5 DOWNGRADE An issue in YASM 1.3.0.86.g9def allows a remote attacker to cause a denial of service via the yasm_section_bcs
CVE-2023-49556 MEDIUM 5.5 DOWNGRADE Buffer Overflow vulnerability in YASM 1.3.0.86.g9def allows a remote attacker to cause a denial of service via

References

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