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Security Digest · Vulnerability record · Known exploited

CVE-2023-4911: GNU C Library Buffer Overflow Vulnerability

Exploited in the wild (CISA KEV). A buffer overflow was discovered in the GNU C Library's dynamic loader ld.so while processing the GLIBCTUNABLES environment variable.

CISA KEV · added 2023-11-21 CVSS 7.8 High EPSS 63.8% · p99

Updated By erroneo.us Security Desk34 references Seen in the digest for Nov 21, 2023

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

  • Yes, if you run GNU GNU C Library. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2023-11-21, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2023-12-12; treat that as the outer limit, not the target.
  • EPSS 63.8%, percentile 99: FIRST’s model estimates a 63.8% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
  • Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.

What it is

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

CISA’s summary

GNU C Library's dynamic loader ld.so contains a buffer overflow vulnerability when processing the GLIBC_TUNABLES environment variable, allowing a local attacker to execute code with elevated privileges.

Weakness type: CWE-122.

Product: GNU GNU C Library · Assigned by: redhat · Published: 2023-10-03

Affected and fixed versions

VendorProductAffected versions (per CVE record)
glibc2.34 < 2.39
Red HatRed Hat Enterprise Linux 8see vendor advisory
Red HatRed Hat Enterprise Linux 8see vendor advisory
Red HatRed Hat Enterprise Linux 8.6 Extended Update Supportsee vendor advisory
Red HatRed Hat Enterprise Linux 9see vendor advisory
Red HatRed Hat Enterprise Linux 9see vendor advisory
Red HatRed Hat Enterprise Linux 9.0 Extended Update Supportsee vendor advisory
Red HatRed Hat Virtualization 4 for Red Hat Enterprise Linux 8see vendor advisory
Red HatRed Hat Virtualization 4 for Red Hat Enterprise Linux 8see vendor advisory
Red HatRed Hat Virtualization 4 for Red Hat Enterprise Linux 8see vendor advisory

Severity scores

Scored byCVSSScoreVector
redhat3.17.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  • Attack vector: local access needed
  • Attack complexity: low
  • Privileges required: low (any account)
  • User interaction: none
  • Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

  • CISA KEV: added 2023-11-21; federal due date 2023-12-12. Known ransomware use: Unknown.
  • CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
  • CISA SSVC assessment: exploitation active, automatable no, technical impact total.
  • FIRST EPSS (model of 2026-10-21): 63.77% probability of exploitation activity in the next 30 days; percentile 99.

Timeline

  • — CVE record published by redhat
  • — Added to CISA’s Known Exploited Vulnerabilities catalog
  • — CISA remediation deadline for US federal agencies
  • — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

  1. RHSA-2023:5453 access.redhat.com
  2. RHSA-2023:5454 access.redhat.com
  3. RHSA-2023:5455 access.redhat.com
  4. RHSA-2023:5476 access.redhat.com
  5. RHSA-2024:0033 access.redhat.com
  6. Listed in CISA KEV notes (sourceware.org) sourceware.org
  7. Listed in CISA KEV notes (access.redhat.com) access.redhat.com
  8. Listed in CISA KEV notes (debian.org) debian.org

Vulnerability records

  1. CVE.org record CVE-2023-4911 cve.org
  2. NVD entry CVE-2023-4911 nvd.nist.gov

Government

  1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

  1. access.redhat.com access.redhat.com
  2. RHBZ#2238352 bugzilla.redhat.com
  3. qualys.com qualys.com
  4. qualys.com qualys.com
  5. exploit-db.com exploit-db.com
  6. packetstormsecurity.com packetstormsecurity.com
  7. packetstormsecurity.com packetstormsecurity.com
  8. seclists.org seclists.org
  9. openwall.com openwall.com
  10. openwall.com openwall.com
  11. openwall.com openwall.com
  12. openwall.com openwall.com
  13. openwall.com openwall.com
  14. openwall.com openwall.com
  15. openwall.com openwall.com
  16. lists.fedoraproject.org lists.fedoraproject.org
  17. lists.fedoraproject.org lists.fedoraproject.org
  18. lists.fedoraproject.org lists.fedoraproject.org
  19. security.gentoo.org security.gentoo.org
  20. security.netapp.com security.netapp.com
  21. cert-portal.siemens.com cert-portal.siemens.com
  22. cert-portal.siemens.com cert-portal.siemens.com
  23. cert-portal.siemens.com cert-portal.siemens.com

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