Exploited. On CISA's list since 2023-11-21.

GNU C Library Buffer Overflow Vulnerability

CVE-2023-4911 · GNU GNU C Library · Published 2023-10-03

How bad would it be?

7.8 out of 10

CVSS rates it high.

How likely is it to be used?

64%

Estimated chance of exploitation in the next 30 days, among the top 1% of all scored flaws (EPSS, 2026-10-29).

Is it already being used?

Yes

CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 1053 days ago (2023-12-12).

What CISA says to do

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

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.

nvd.nist.gov

What the flaw is

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.

From the NVD.

Fixes and advisories

bugzilla.redhat.comPatch
bugzilla.redhat.comPatch

Learn this

Explore this week’s weaknesses and all learning topics

Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.

Heap buffer overflow

A write runs past allocated heap storage and can damage neighbouring data.

CWE-122 · CISA KEV; NVD record: secalert@redhat.com

Video course · Free course. C programming and memory concepts are useful; covers several weakness types.

Watch the course at OpenSecurityTraining2 How it is prevented

Out-of-bounds write

A program writes outside the memory region it is allowed to use.

CWE-787 · NVD record: nvd@nist.gov

Video course · Free course. C programming and memory concepts are useful; covers several weakness types.

Watch the course at OpenSecurityTraining2 How it is prevented

CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.

On SentryFeed

No story in the last 14 days has mentioned it.

Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.