CVE-2021-20254 Information disclosure in samba
Medium 6.8
Published
Updated
Check this codebase for CVE-2021-20254 and fix it if it is affected.
What it is: CVE-2021-20254 is a medium-severity vulnerability in Debian Debian Linux, published on 5 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-20254 in the wild and no public exploit code.
Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2021-20254/ (Markdown: https://insights.sbomify.com/CVE-2021-20254/index.md)
A flaw in Samba's group mapping allows reading beyond array bounds, potentially exposing or modifying user group membership data.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-20254?
CVE-2021-20254 is a medium-severity vulnerability in Debian Debian Linux, published on 5 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-125
Which versions are affected by CVE-2021-20254?
It affects 4 products.
Linux distribution packages (40)
libsmbclient-devel AlmaLinux:8 | All versions | 4.13.3-5.el8_4 |
libwbclient-devel AlmaLinux:8 | All versions | 4.13.3-5.el8_4 |
samba-devel AlmaLinux:8 | All versions | 4.13.3-5.el8_4 |
libsmbclient Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
libsmbclient-devel Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
libwbclient Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
libwbclient-devel Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-client Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-client-libs Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-common Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-common-libs Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-common-tools Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-dc Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-dc-libs Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-debuginfo Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-devel Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-krb5-printing Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-libs Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-pidl Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-python Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-python-test Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-test Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-test-libs Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-vfs-glusterfs Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-winbind Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-winbind-clients Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-winbind-krb5-locator Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
samba-winbind-modules Red Hat:enterprise_linux:7::client | All versions | 0:4.10.16-15.el7_9 |
libsmbclient-devel Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
libwbclient-devel Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-dc Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-dc-libs Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-debuginfo Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-devel Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-krb5-printing Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-pidl Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-python Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
samba-python-test Red Hat:enterprise_linux:7::computenode | All versions | 0:4.10.16-15.el7_9 |
Products include Debian Debian Linux, Fedoraproject Fedora, Redhat Enterprise Linux, Samba Samba.
How do I fix CVE-2021-20254?
Apply the vendor's patch.
Is CVE-2021-20254 being exploited?
There is no known exploitation of CVE-2021-20254 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as ALPINE-CVE-2021-20254, ALSA-2021:4058, AZL-36999, AZL-7352, DEBIAN-CVE-2021-20254, ECHO-3f66-59c9-67b2 and 15 more.