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

> A local attacker can exploit a buffer overflow in the dynamic loader to execute code with elevated privileges via malicious environment variables.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Yes, since 21 Nov 2023 (CISA KEV)
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Oct 2023
- **Updated:** 14 Oct 2026
- **Also known as:** AZL-31117, AZL-34733, BELL-CVE-2023-4911, CLSA-2023-1698312626, DEBIAN-CVE-2023-4911, DSA-5514-1, GHSA-m77w-6vjw-wh2f, MGASA-2023-0286, MINI-5jjw-w7wp-vgf4, OESA-2023-1723, OESA-2023-1724, OESA-2023-1725, RHSA-2023:5454, RHSA-2023:5476, RHSA-2024:0033, UBUNTU-CVE-2023-4911, USN-6409-1, openSUSE-SU-2024:13294-1

## What is CVE-2023-4911?

CVE-2023-4911 is a high-severity memory corruption vulnerability in Canonical Ubuntu Linux, published on 3 Oct 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### 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.

Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2023-4911?

It affects 39 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `compat-libpthread-nonshared` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-benchtests-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-common-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-debugsource` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-gconv-extra-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-utils` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc-utils-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `libnsl-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `nscd-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `nss_db-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `nss_hesiod-debuginfo` | Red Hat:rhel_eus:8.6::appstream | All versions | 0:2.28-189.6.el8_6 |
| `glibc` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-all-langpacks` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-benchtests-debuginfo` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-common` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-common-debuginfo` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-debuginfo` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-debugsource` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-devel` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-doc` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-gconv-extra` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-gconv-extra-debuginfo` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-headers` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-aa` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-af` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-agr` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-ak` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-am` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-an` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-anp` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-ar` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-as` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-ast` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-ayc` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-az` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-be` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-bem` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-ber` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |
| `glibc-langpack-bg` | Red Hat:rhel_eus:8.6::baseos | All versions | 0:2.28-189.6.el8_6 |

Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Gnu Glibc, Netapp Bootstrap Os, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware, Netapp Ontap Select Deploy Administration Utility, Redhat Codeready Linux Builder, Redhat Codeready Linux Builder Eus, Redhat Codeready Linux Builder for Arm64, Redhat Codeready Linux Builder for Arm64 Eus, Redhat Codeready Linux Builder for Ibm Z Systems, Redhat Codeready Linux Builder for Ibm Z Systems Eus, Redhat Codeready Linux Builder for Power Little Endian, Redhat Codeready Linux Builder for Power Little Endian Eus, Redhat Enterprise Linux and 19 more.

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

Apply the vendor's patch. US federal agencies must fix it by 12 Dec 2023.

## Is CVE-2023-4911 being exploited?

Yes. Attackers have exploited CVE-2023-4911 in the wild since at least 21 Nov 2023.

Public exploit code:

- PoC for CVE-2023-4911 (github_poc): https://github.com/leesh3288/CVE-2023-4911
- CVE-2023-4911 proof of concept (github_poc): https://github.com/RickdeJager/CVE-2023-4911
- Exploit tool for CVE-2023-4911, targeting the 'Looney Tunables' glibc vulnerability in various Linux distributions. (github_poc): https://github.com/chaudharyarjun/LooneyPwner
- https://github.com/hadrian3689/looney-tunables-CVE-2023-4911 (github_poc): https://github.com/hadrian3689/looney-tunables-CVE-2023-4911
- CVE-2023-4911 (github_poc): https://github.com/ruycr4ft/CVE-2023-4911
- Looney Tunables Local privilege escalation (CVE-2023-4911) workshop (github_poc): https://github.com/KernelKrise/CVE-2023-4911

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-4911 and fix it if it is affected.

What it is: CVE-2023-4911 is a high-severity memory corruption vulnerability in Canonical Ubuntu Linux, published on 3 Oct 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2023-4911 in the wild since at least 21 Nov 2023.

Affected product: Canonical Ubuntu 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-2023-4911/ (Markdown: https://insights.sbomify.com/CVE-2023-4911/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-4911
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-4911
- OSV: https://osv.dev/vulnerability/CVE-2023-4911

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-4911/
Summaries are generated and may contain mistakes; the official description above is the record.