External risk intelligence

GNU C Library Call Graph Monitor Buffer Overflow

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-0687

This vulnerability exists within the GNU C Library (glibc), specifically in the Call Graph Monitor component used during application profiling or build-time instrumentation. It is not a network-exposed service or interface. The affected code is linked into local applications and requires specific, typically internal or developer-controlled inputs to trigger, making public internet exposure and reachability effectively non-existent.

Buffer Overflow

Gnu Glibc

before 2.38

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 critical vulnerability has been identified in the GNU C Library affecting its Call Graph Monitor function, potentially leading to a buffer overflow. While the vulnerability's actual existence is currently in doubt, its theoretical impact could be significant if exploited. The primary concern at this stage is to confirm if our systems utilize this specific component and are thus potentially exposed.

A software flaw could allow unauthorized control.
Its existence is currently unconfirmed but critical if real.
Verify if this component is in use to assess risk.

Attack Path

How an attacker could exploit the issue

An attacker could potentially reach this vulnerability by manipulating inputs related to the running application's profiling data when the GNU C Library is configured with its Call Graph Monitor. This manipulation, if successful, could lead to a buffer overflow within the `__monstartup` function. However, the existence of this vulnerability is currently doubted, and triggering it likely requires specific, controlled inputs that are not typically exposed to external attackers.

Requires application profiling or instrumentation.
Triggered by specific profiling data inputs.
Leads to buffer overflow.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability in the GNU C Library's Call Graph Monitor could potentially lead to a buffer overflow when processing specific addresses from applications compiled with profiling enabled, under conditions where these inputs are controlled or compromised.

Application profiling data.
When trusted or controlled inputs are manipulated.
Application stability and integrity may be affected.

Operational Fix

Recommended remediation, mitigation, and detection steps

The GNU C Library's Call Graph Monitor component is likely managed by platform or development teams. Since the vulnerability's existence is currently doubted and requires specific, controlled inputs for exploitation, the first practical step is to confirm its presence in the environment and assess its actual risk.

Platform or development teams own the issue.
Verify if affected profiling features are enabled.
Plan remediation if profiler use is confirmed.

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 the Call Graph Monitor?

The GNU C Library, or glibc, provides the core system-level functions used by nearly all programs on Linux-based operating systems. The Call Graph Monitor is a specialized component within this library used by developers to profile application performance and trace function calls during the build or testing phase.

How does CVE-2023-0687 cause a buffer overflow?

This vulnerability is classified as CWE-120, a classic buffer overflow weakness. It theoretically occurs in the __monstartup function if it handles memory incorrectly while processing instrumentation data. In this context, the flaw suggests that malicious or malformed memory addresses could overrun designated buffers, potentially destabilizing the application.

What triggers this vulnerability?

The bug requires an application to be specifically compiled or configured with the Call Graph Monitor enabled. It is not triggered by standard network traffic or typical user inputs. Exploitation would require control over the internal profiling data used by the application, which is typically restricted to local, trusted environments.

Is my environment at risk from this glibc flaw?

Halo Surface Signal indicates that this risk is very unlikely. Because the affected component is a build-time or profiling utility rather than a network-exposed service, it is not reachable via the internet. It is rarely part of standard production-facing interfaces, significantly lowering the practical threat level.

How should I respond to CVE-2023-0687?

Your first step is to confirm if any applications in your environment are actively using the Call Graph Monitor feature. Since the existence of this flaw is currently doubted, focus on identifying where this library component is enabled. If you identify such systems, consult with your development teams to determine if the profiling features are necessary or can be disabled.

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.