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NVD / CVE Program· CNA redhat

CVE-2021-20254: A flaw was found in samba.

MediumCVSS 6.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.6% (FIRST EPSS); higher than 76.3% of all records.
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Azure Linux 3.0 ARM 4.18.3-1; Azure Linux 3.0 x64 4.18.3-1.
  • Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Azure Linux 3.0 ARM 4.18.3-1; Azure Linux 3.0 x64 4.18.3-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A flaw was found in samba. The Samba smbd file server must map Windows group identities (SIDs) into unix group ids (gids). The code that performs this had a flaw that could allow it to read data beyond the end of the array in the case where a negative cache entry had been added to the mapping cache. This could cause the calling code to return those values into the process token that stores the group membership for a user. The highest threat from this vulnerability is to data confidentiality and integrity.

Published
May 5, 2021
Updated
Jun 16, 2026
EPSS
1.6% · 76th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.6%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
sambasamba
fedoraprojectfedora
redhatenterprise linux
debiandebian linux

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a samba

    • samba 4.14.1, samba 4.13.6, samba 4.12.13affected
Affected versions · NVD (8)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux9.0
  • fedoraproject fedora32
  • fedoraproject fedora33
  • redhat enterprise linux7.0
  • redhat enterprise linux8.0
  • samba samba4.14.0 and later · before 4.14.4
  • samba samba3.6.0 and later · before 4.12.15
  • samba samba4.13.0 and later · before 4.13.8

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8libsmbclient-develbefore 4.13.3-5.el8_44.13.3-5.el8_4
AlmaLinux:8libwbclient-develbefore 4.13.3-5.el8_44.13.3-5.el8_4
AlmaLinux:8samba-develbefore 4.13.3-5.el8_44.13.3-5.el8_4
Alpine:v3.12sambafrom 3.6.0 · before 4.12.15-r04.12.15-r0
Alpine:v3.13sambafrom 3.6.0 · before 4.13.8-r04.13.8-r0
Alpine:v3.14sambafrom 3.6.0 · before 4.14.4-r04.14.4-r0
Debian:12sambabefore 2:4.13.5+dfsg-22:4.13.5+dfsg-2
Debian:9sambabefore 2:4.5.16+dfsg-1+deb9u42:4.5.16+dfsg-1+deb9u4
openSUSE:Leap 15.2sambabefore 4.11.14+git.247.8c858f7ee14-lp152.3.19.14.11.14+git.247.8c858f7ee14-lp152.3.19.1
openSUSE:Leap 15.3sambabefore 4.13.6+git.211.555d60b24ba-3.7.14.13.6+git.211.555d60b24ba-3.7.1
Red Hat:enterprise_linux:7::clientlibsmbclientbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientlibsmbclient-develbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientlibwbclientbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientlibwbclient-develbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsambabefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-clientbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-client-libsbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-commonbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-common-libsbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-common-toolsbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-dcbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-dc-libsbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-debuginfobefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9
Red Hat:enterprise_linux:7::clientsamba-develbefore 0:4.10.16-15.el7_90:4.10.16-15.el7_9

+96

Same product

samba: all records

Other highest-scoring records for the same primary product.

  • CVE-2017-7494Samba since version 3.5.0 and before 4.6.4, 4.5.10 and 4.4.14 is vulnerable to remote code execution vulnerability, allowing a malicious…KEV
    99Now
  • CVE-2015-0240The Netlogon server implementation in smbd in Samba 3.5.x and 3.6.x before 3.6.25, 4.0.x before 4.0.25, 4.1.x before 4.1.17, and 4.2.x…
    66This week
  • CVE-2003-0085Buffer overflow in the SMB/CIFS packet fragment re-assembly code for SMB daemon (smbd) in Samba before 2.2.8, and Samba-TNG before 0.3.1…
    66This week

Published before and after this one in the same product

  • ← EarlierCVE-2020-14383Dec 1, 2020 · A flaw was found in samba's DNS server.
    27Monitor
  • ← EarlierCVE-2020-14318Dec 3, 2020 · A flaw was found in the way samba handled file and directory permissions.
    17Monitor
  • Later →CVE-2021-20277May 12, 2021 · A flaw was found in Samba's libldb.
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Azure Linux 3.0 ARM4.18.3-1 · sambaMicrosoft (MSRC)
Azure Linux 3.0 x644.18.3-1 · sambaMicrosoft (MSRC)
almalinux:libsmbclient-devel4.13.3-5.el8_4 · AlmaLinux:8Package registry (OSV)
almalinux:libwbclient-devel4.13.3-5.el8_4 · AlmaLinux:8Package registry (OSV)
almalinux:samba-devel4.13.3-5.el8_4 · AlmaLinux:8Package registry (OSV)
alpine:samba4.12.15-r0 · Alpine:v3.12Package registry (OSV)
debian:samba2:4.13.5+dfsg-2 · Debian:12Package registry (OSV)
opensuse:samba4.11.14+git.247.8c858f7ee14-lp152.3.19.1 · openSUSE:Leap 15.2Package registry (OSV)
red hat:libsmbclient0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:libwbclient0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-client0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-client-libs0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-common0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-common-libs0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-common-tools0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-debuginfo0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-krb5-printing0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-libs0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:samba-winbind0:4.10.16-15.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
rocky linux:samba0:4.13.3-5.el8_4 · Rocky Linux:8Package registry (OSV)
suse:ldb2.2.1-4.3.1 · SUSE:Enterprise Storage 7Package registry (OSV)
suse:samba4.10.18+git.269.dd608524c88-3.27.1 · SUSE:Linux Enterprise High Availability Extension 12 SP5Package registry (OSV)
suse:samba-doc3.6.3-94.34.1 · SUSE:Linux Enterprise Point of Sale 11 SP3Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records