External risk intelligence

GNU glibc 2.37 Buffer Overflow in sprintf

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-25139

This vulnerability exists in the GNU C Library (glibc), a low-level foundational software library used by virtually all applications on a system. It is not an internet-facing service, appliance, or application itself. While applications using glibc may be exposed to the internet, the library itself is a local component, making direct public-internet-facing exposure of this specific surface very unlikely.

Out-of-bounds Write

Gnu Glibc

2.37

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A recently identified flaw in the GNU C Library, a core component used by many applications, could allow for unauthorized data access or manipulation. This issue stems from a specific function within the library that handles numerical string conversions, where an exact buffer size could lead to an overflow, potentially impacting systems that rely on this library. The main concern at this time is confirming whether our environment is exposed to this vulnerability.

A library flaw could permit unauthorized data access.
It affects foundational software used by many applications.
Confirm relevance and exposure to understand potential impact.

Attack Path

How an attacker could exploit the issue

An attacker could reach this vulnerability through the `sprintf` function within the GNU C Library (glibc). This function, when processing specific numeric formats with exact buffer sizes, can write beyond allocated memory. This could potentially lead to critical system compromise.

No specific access required.
Triggered by formatting numbers with padding.
Risk of out-of-bounds write.

Live Threat

Current exploitation, exposure, and threat context

When the GNU C Library attempts to format numbers with thousands separators and padding, a buffer overflow could occur if the destination buffer is exactly the size needed for the formatted string. This might lead to an out-of-bounds write, potentially impacting system stability and integrity.

Affects system memory and program execution.
Buffer overflow during number formatting.
May cause application crashes or instability.

Operational Fix

Recommended remediation, mitigation, and detection steps

Real-world ownership of this GNU C Library (glibc) vulnerability likely falls to infrastructure, platform, or operating system teams responsible for maintaining the core system libraries. The first practical step is to identify all systems running the affected glibc version, determine their exposure and criticality, and then locate the accountable application or system owner to plan remediation.

Infrastructure and Platform Teams own remediation.
Verify affected systems and their criticality.
Plan remediation based on risk assessment.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the GNU C Library (glibc) and why is it important?

The GNU C Library, or glibc, is a foundational software library that acts as a bridge between computer programs and the operating system's kernel. It provides essential building blocks, such as basic input/output, memory management, and string manipulation routines. Because nearly every application on a Linux-based system relies on glibc to execute common tasks, it is considered a core component for overall system functionality.

What is the nature of the buffer overflow vulnerability in CVE-2023-25139?

This vulnerability is classified as CWE-787, which is an out-of-bounds write flaw. It specifically occurs in the `sprintf` function when the library tries to format a number with thousands separators and specific padding. If the destination buffer is sized exactly to the length of the final string, the function fails to account for the necessary space, causing it to write data beyond the intended memory boundaries.

How is this glibc vulnerability triggered?

The flaw is triggered when an application calls `sprintf` to process a numeric value using formatting flags that require padding and thousands separators. If the destination buffer allocated by the developer is exactly the minimum size required, the library writes data into unauthorized memory. This does not occur if the buffer is larger than the exact requirement, or if the number formatting logic does not involve these specific combinations of padding and separators.

Why is internet-facing exposure unlikely for this specific library issue?

According to Halo Surface Signal, this vulnerability resides in a low-level library rather than a standalone network service or web application. While software that uses glibc might be connected to the internet, the library itself is a local component embedded deep within the system. Therefore, direct public access to this specific memory flaw is considered very unlikely.

What should I do if I am running the affected glibc version?

The primary response is to coordinate with infrastructure or platform teams to identify where glibc 2.37 is currently deployed. Since this is a core system component, remediation is typically handled via operating system updates provided by your distribution vendor. Prioritize inventory management to understand which applications rely on this version, then monitor for official patches that address the memory allocation behavior in `sprintf`.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.