# What is CVE-2023-4911?

> CVE-2023-4911 is a high-severity flaw (CVSS 7.8) in Glibc from Gnu, published on 3 October 2023. It is on the list of flaws known to be exploited, so criminals are already using it. The latest forecast puts its chance of use in the next 30 days at 64%. If you run an affected version, patch it first.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2023-4911

## At a glance

- **Verdict:** Fix this now. Attackers are using this flaw today. If you run an affected version, it goes to the top of your list.
- **Precursor Intelligence risk score:** 71 out of 100 (High); action: Emergency patch. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 7.8 out of 10)
- **Known to be exploited:** Yes, it is on the government list of flaws known to be exploited
- **Chance of use in the next 30 days:** 64% (latest exploit-likelihood forecast)
- **Published:** 3 October 2023
- **Record last updated:** 21 October 2025
- **Main product:** Glibc from Gnu
- **Affected products:** 33

## What is CVE-2023-4911? In plain terms

An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### The official description

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.

### What kind of flaw is it?

- CWE-122: Heap-based Buffer Overflow
- CWE-787: Out-of-bounds Write

### How an attack on it works

- Where an attacker can be: Already on the device
- How hard it is to pull off: Easy: no special conditions
- Login needed first: An ordinary user account
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can read data, change data and take it offline

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

## Is CVE-2023-4911 being exploited? Yes

Attackers are already using it. It is on the government list of flaws known to be exploited, and the latest forecast puts the chance of it being used in the next 30 days at 64%.

Exploit likelihood over the last 7 days: 64%, 64%, 64%, 64%, 64%, 64%, 64%.

### Timeline

- 3 October 2023: Published
- 11 June 2025: Exploit likelihood fell
- 21 October 2025: Record last updated
- 19 November 2025: Exploit likelihood jumped

### How Precursor Intelligence ranks it

CVE-2023-4911 scores **71 out of 100 (High)**, with the action "Emergency patch".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2023-4911?

The published record lists 33 products. Versions are as published: "2.34 to before 2.39" means from 2.34 up to, but not including, 2.39.

- [Glibc](https://www.precursorintelligence.com/product/gnu/glibc) by [Gnu](https://www.precursorintelligence.com/vendors/gnu) (Application): 2.34 to before 2.39
- [Codeready Linux Builder Eus](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 8.6, 9.2, 9.4
- [Codeready Linux Builder for Arm64 Eus](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_for_arm64_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 8.6, 9.2_aarch64, 9.4_aarch64
- [Codeready Linux Builder for Ibm Z Systems Eus](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_for_ibm_z_systems_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 8.6, 9.2_s390x, 9.4_s390x
- [Codeready Linux Builder for Power Little Endian Eus](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_for_power_little_endian_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 8.6, 9.2_ppc64le, 9.4_ppc64le
- [Enterprise Linux Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.6, 9.2, 9.4
- [Enterprise Linux for Arm 64 Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_arm_64_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.6_aarch64, 9.2_aarch64, 9.4_aarch64
- [Enterprise Linux Server Aus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server_aus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.6, 9.2, 9.4
- [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 37, 38, 39
- [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 11.0, 12.0
- [Enterprise Linux](https://www.precursorintelligence.com/product/redhat/enterprise_linux) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.0, 9.0
- [Enterprise Linux for Ibm Z Systems Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_ibm_z_systems_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.2_s390x, 9.4_s390x
- [Enterprise Linux for Power Little Endian Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_power_little_endian_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.2_ppc64le, 9.4_ppc64le
- [Enterprise Linux Server for Power Little Endian Update Services for Sap Solutions](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.2_ppc64le, 9.4_ppc64le
- [Ubuntu Linux](https://www.precursorintelligence.com/product/canonical/ubuntu_linux) by [Canonical](https://www.precursorintelligence.com/vendors/canonical) (Operating system): 22.04, 23.04
- [Codeready Linux Builder](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 9.0
- [Codeready Linux Builder for Arm64](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_for_arm64) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 9.0_aarch64
- [Codeready Linux Builder for Ibm Z Systems](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_for_ibm_z_systems) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 9.0_s390x
- [Codeready Linux Builder for Power Little Endian](https://www.precursorintelligence.com/product/redhat/codeready_linux_builder_for_power_little_endian) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 9.0_ppc64le
- [Enterprise Linux for Arm 64](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_arm_64) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.0_aarch64
- [Enterprise Linux for Ibm Z Systems](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_ibm_z_systems) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.0_s390x
- [Enterprise Linux for Ibm Z Systems Eus S390x](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_ibm_z_systems_eus_s390x) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.6
- [Enterprise Linux for Power Big Endian Eus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_power_big_endian_eus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.6_ppc64le
- [Enterprise Linux for Power Little Endian](https://www.precursorintelligence.com/product/redhat/enterprise_linux_for_power_little_endian) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 9.0_ppc64le
- [Enterprise Linux Server Tus](https://www.precursorintelligence.com/product/redhat/enterprise_linux_server_tus) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Operating system): 8.6
- [H300s Firmware](https://www.precursorintelligence.com/product/netapp/h300s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H410c Firmware](https://www.precursorintelligence.com/product/netapp/h410c_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H410s Firmware](https://www.precursorintelligence.com/product/netapp/h410s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H500s Firmware](https://www.precursorintelligence.com/product/netapp/h500s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [H700s Firmware](https://www.precursorintelligence.com/product/netapp/h700s_firmware) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Operating system): version not specified
- [Ontap Select Deploy Administration Utility](https://www.precursorintelligence.com/product/netapp/ontap_select_deploy_administration_utility) by [Netapp](https://www.precursorintelligence.com/vendors/netapp) (Application): version not specified
- [Virtualization](https://www.precursorintelligence.com/product/redhat/virtualization) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 4.0
- [Virtualization Host](https://www.precursorintelligence.com/product/redhat/virtualization_host) by [Red Hat](https://www.precursorintelligence.com/vendors/redhat) (Application): 4.0

## How do I fix CVE-2023-4911?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisory first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Check it wasn’t used before you patched.** Because criminals are already using this flaw, look for signs of a break-in on affected systems using the vendor’s guidance.

### References

- [bugzilla.redhat.com](https://bugzilla.redhat.com/show_bug.cgi?id=2238352) (Issue tracking, Patch)
- [access.redhat.com](https://access.redhat.com/errata/RHBA-2024:2413) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2023:5453) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2023:5454) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2023:5455) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2023:5476) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/errata/RHSA-2024:0033) (Third-party advisory)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2023-4911) (Third-party advisory)
- [qualys.com](https://www.qualys.com/2023/10/03/cve-2023-4911/looney-tunables-local-privilege-escalation-glibc-ld-so.txt) (Exploit, Third-party advisory)
- [qualys.com](https://www.qualys.com/cve-2023-4911/) (Third-party advisory)
- [packetstormsecurity.com](http://packetstormsecurity.com/files/174986/glibc-ld.so-Local-Privilege-Escalation.html) (Exploit, Third-party advisory, Vulnerability database)
- [packetstormsecurity.com](http://packetstormsecurity.com/files/176288/Glibc-Tunables-Privilege-Escalation.html) (Exploit, Third-party advisory, Vulnerability database)
- [seclists.org](http://seclists.org/fulldisclosure/2023/Oct/11) (Exploit, Mailing list, Third-party advisory)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/03/2) (Exploit, Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/03/3) (Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/05/1) (Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/13/11) (Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/14/3) (Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/14/5) (Mailing list)
- [openwall.com](http://www.openwall.com/lists/oss-security/2023/10/14/6) (Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4DBUQRRPB47TC3NJOUIBVWUGFHBJAFDL/) (Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DFG4P76UHHZEWQ26FWBXG76N2QLKKPZA/) (Mailing list)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NDAQWHTSVOCOZ5K6KPIWKRT3JX4RTZUR/) (Mailing list)
- [security.gentoo.org](https://security.gentoo.org/glsa/202310-03) (Third-party advisory)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20231013-0006/) (Third-party advisory)
- [debian.org](https://www.debian.org/security/2023/dsa-5514) (Mailing list)
- [cisa.gov](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-4911)

## Questions

### What is CVE-2023-4911?

CVE-2023-4911 is a high-severity flaw in Glibc from Gnu, published on 3 October 2023. An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### How serious is CVE-2023-4911?

It scores 7.8 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2023-4911 is 71 out of 100, which is High. Its action is "Emergency patch". Attackers are using this flaw today. If you run an affected version, it goes to the top of your list.

### Is CVE-2023-4911 being exploited?

Attackers are already using it. It is on the government list of flaws known to be exploited, and the latest forecast puts the chance of it being used in the next 30 days at 64%.

### Which versions does CVE-2023-4911 affect?

For Glibc from Gnu: 2.34 to before 2.39. The record lists 33 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2023-4911?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. Because criminals are already using it, also check affected systems for signs of a break-in.

## Does CVE-2023-4911 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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