dbcve.org
Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 12 Dec 2023.
FedoraOperating system · Fedoraproject

CVE-2023-4911

HIGH · 7.8 CVSS v3.1 Published 2023-10-03
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
96/100
Remediation priority · Urgent
In the wild High EPSS Public exploit Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A buffer overflow was discovered in the GNU C Library's dynamic loader ld.so while processing the GLIBC_TUNABLES environment variable. This issue could allow a local attacker to use maliciously crafted GLIBC_TUNABLES environment variables when launching binaries with SUID permission to execute code with elevated privileges.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A buffer overflow in the GNU C Library's dynamic loader (ld.so) occurs when processing the GLIBC_TUNABLES environment variable. By crafting a malicious GLIBC_TUNABLES value and launching SUID binaries with this environment variable set, a local attacker can achieve arbitrary code execution with elevated privileges.

MitigationUpgrade glibc to a patched version (2.37+ or 2.34+ with backported fix). As a temporary workaround, unset GLIBC_TUNABLES in the environment for SUID binaries or use systemd's ProtectSystem=full with ProtectHome=read-only to restrict environment variable injection.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FedoraOperating system
Affected:= 37= 38= 39
Codeready Linux BuilderApplication
Affected:= 9.0
Codeready Linux Builder EusApplication
Affected:= 8.6= 9.2= 9.4= 9.6
Codeready Linux Builder For Arm64Application
Affected:= 9.0_aarch64
Codeready Linux Builder For Arm64 EusApplication
Affected:= 8.6= 9.2_aarch64= 9.4_aarch64= 9.6_aarch64
Codeready Linux Builder For Ibm Z SystemsApplication
Affected:= 9.0_s390x
Codeready Linux Builder For Ibm Z Systems EusApplication
Affected:= 8.6= 9.2_s390x= 9.4_s390x= 9.6_s390x
Codeready Linux Builder For Power Little EndianApplication
Affected:= 9.0_ppc64le

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify your Linux distribution and version
    Run 'cat /etc/os-release' or 'hostnamectl' to determine if you are running Fedora 37, 38, or 39, or a Red Hat Codeready Linux Builder variant
    Affected if The distribution matches one of the listed affected Fedora or Codeready versions (37, 38, 39 for Fedora; 9.0, 8.6, 9.2, 9.4, 9.6 and associated architecture variants for Codeready)
  2. Determine the installed glibc version
    Run 'ldd --version' or 'rpm -q glibc' to obtain the glibc package version
    Affected if The glibc version falls within the vulnerable version range for your distribution (compare your installed version to the affected ranges)
  3. Check for GLIBC_TUNABLES environment variable
    Run 'env | grep GLIBC_TUNABLES' to see if this variable is set in the current environment
    Affected if GLIBC_TUNABLES is present and contains user-controlled values - this variable triggers the vulnerable code path in ld.so when SUID binaries execute
  4. Identify SUID binaries on the system
    Run 'find / -perm -4000 -type f 2>/dev/null' to list all SUID binaries
    Affected if SUID binaries exist on the system - these are the targets that would execute with elevated privileges and trigger the vulnerability if GLIBC_TUNABLES is set

You are affected if your system runs an affected Fedora or Red Hat Codeready Linux Builder version AND has a vulnerable glibc version AND has SUID binaries present AND the GLIBC_TUNABLES environment variable can be passed to SUID binary execution.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch bugzilla.redhat.com →
Interim mitigation

Upgrade glibc to a patched version (2.37+ or 2.34+ with backported fix). As a temporary workaround, unset GLIBC_TUNABLES in the environment for SUID binaries or use systemd's ProtectSystem=full with ProtectHome=read-only to restrict environment variable injection.

Recommended fix High confidence

glibc 2.36-14.fc37 (Fedora 37), glibc 2.37-7.fc38 (Fedora 38), glibc 2.38-11.fc39 (Fedora 39), or corresponding glibc updates for Red Hat/Codeready Linux Builder

  1. 1. Update the system package cache: sudo dnf check-update (Fedora) or sudo yum check-update (RHEL/Codeready)
  2. 2. Upgrade the glibc package: sudo dnf upgrade glibc (Fedora) or sudo yum update glibc (RHEL/Codeready)
  3. 3. Verify the installed glibc version matches or exceeds the fixed release (e.g., glibc 2.36-14.fc37 for Fedora 37, glibc 2.37-7.fc38 for Fedora 38, glibc 2.38-11.fc39 for Fedora 39)
  4. 4. Reboot the system to ensure the new glibc is loaded into memory
  5. 5. After reboot, verify the vulnerability is resolved by checking: glibc --version
Caveat The glibc upgrade is a low-risk system library update; however, some older binaries statically linked against older glibc versions may require recompilation if compatibility issues arise after the upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fedora Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,760
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,616.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2023-4911 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-4911 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data