---
title: "CVE-2023-4911: GNU C Library Buffer Overflow Vulnerability"
url: https://erroneo.us/security/cve/CVE-2023-4911/
description: "CVE-2023-4911 (GNU GNU C Library): Exploited in the wild (CISA KEV). A buffer overflow was discovered in the GNU C Library's dynamic loader ld.so while…"
type: vulnerability-record
section: "Security Digest"
date_published: 2023-10-03
date_modified: 2026-10-14
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2023-4911"
kev: true
cvss: 7.8
epss: 0.63769
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- 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.

## Affected products (CVE record)

-  glibc: 2.34 < 2.39
- Red Hat Red Hat Enterprise Linux 8: see advisory
- Red Hat Red Hat Enterprise Linux 8: see advisory
- Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support: see advisory
- Red Hat Red Hat Enterprise Linux 9: see advisory
- Red Hat Red Hat Enterprise Linux 9: see advisory
- Red Hat Red Hat Enterprise Linux 9.0 Extended Update Support: see advisory
- Red Hat Red Hat Virtualization 4 for Red Hat Enterprise Linux 8: see advisory
- Red Hat Red Hat Virtualization 4 for Red Hat Enterprise Linux 8: see advisory
- Red Hat Red Hat Virtualization 4 for Red Hat Enterprise Linux 8: see advisory

## Severity

- redhat CVSS 3.1: 7.8 `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- 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.

## Sources

- [RHSA-2023:5453](https://access.redhat.com/errata/RHSA-2023:5453)
- [RHSA-2023:5454](https://access.redhat.com/errata/RHSA-2023:5454)
- [RHSA-2023:5455](https://access.redhat.com/errata/RHSA-2023:5455)
- [RHSA-2023:5476](https://access.redhat.com/errata/RHSA-2023:5476)
- [RHSA-2024:0033](https://access.redhat.com/errata/RHSA-2024:0033)
- [Listed in CISA KEV notes (sourceware.org)](https://sourceware.org/git/?p=glibc.git)
- [Listed in CISA KEV notes (access.redhat.com)](https://access.redhat.com/security/cve/cve-2023-4911)
- [Listed in CISA KEV notes (debian.org)](https://www.debian.org/security/2023/dsa-5514)
- [CVE.org record CVE-2023-4911](https://www.cve.org/CVERecord?id=CVE-2023-4911)
- [NVD entry CVE-2023-4911](https://nvd.nist.gov/vuln/detail/CVE-2023-4911)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-4911)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2023-4911)
- [RHBZ#2238352](https://bugzilla.redhat.com/show_bug.cgi?id=2238352)
- [qualys.com](https://www.qualys.com/2023/10/03/cve-2023-4911/looney-tunables-local-privilege-escalation-glibc-ld-so.txt)
- [qualys.com](https://www.qualys.com/cve-2023-4911/)
- [exploit-db.com](https://www.exploit-db.com/exploits/52479)
- [packetstormsecurity.com](http://packetstormsecurity.com/files/174986/glibc-ld.so-Local-Privilege-Escalation.html)
- [packetstormsecurity.com](http://packetstormsecurity.com/files/176288/Glibc-Tunables-Privilege-Escalation.html)
- [seclists.org](http://seclists.org/fulldisclosure/2023/Oct/11)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/03/2)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/03/3)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/05/1)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/13/11)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/14/3)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/14/5)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/14/6)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4DBUQRRPB47TC3NJOUIBVWUGFHBJAFDL/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DFG4P76UHHZEWQ26FWBXG76N2QLKKPZA/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NDAQWHTSVOCOZ5K6KPIWKRT3JX4RTZUR/)
- [security.gentoo.org](https://security.gentoo.org/glsa/202310-03)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20231013-0006/)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/html/ssa-831302.html)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/html/ssa-794697.html)
- [cert-portal.siemens.com](https://cert-portal.siemens.com/productcert/html/ssa-082556.html)

---
Source page: https://erroneo.us/security/cve/CVE-2023-4911/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt