External risk intelligence

Nettle library memory corruption vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-36660

Nettle is a low-level cryptographic library used as a dependency by other software, not a standalone product or service. It does not have a public-facing deployment pattern of its own; rather, it is integrated into the build-time or runtime environment of various applications. Because it is a library rather than an edge service or application, it is not directly reachable via the public internet.

Out-of-bounds Write

Nettle Project Nettle

3.9

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

This vulnerability involves memory corruption in a cryptographic library used by other software. While the library itself is not directly exposed, its impact could be significant if compromised, potentially affecting the integrity and confidentiality of data handled by the applications that rely on it. The primary concern at this stage is to confirm if our environment utilizes software that depends on this specific library.

A library flaw can corrupt memory.
Confirm if our software uses this library.
Understand exposure for dependent applications.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted data over a network to a system using a vulnerable version of the Nettle library. This could lead to a crash or potential corruption of memory, impacting the confidentiality, integrity, and availability of the affected system.

Unauthenticated network access required.
Vulnerable OCB feature in the library.
Memory corruption leading to system compromise.

Live Threat

Current exploitation, exposure, and threat context

Memory corruption in the OCB feature could impact systems using Nettle libraries, potentially leading to denial-of-service or code execution when this feature is used.

Corrupted memory in library functions.
Triggered by specific cryptographic operations.
System instability or unauthorized code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

Real-world ownership of this vulnerability rests with the teams responsible for the applications and systems that utilize the libnettle library. Initially, focus should be on identifying all instances where libnettle is deployed, determining their reachability and criticality to business operations, and then assigning the issue to the accountable application or platform owner. Planning remediation will depend on these findings and the specific maintenance schedules of the affected systems.

Application or platform owners should take ownership.
Verify where libnettle is deployed and used.
Plan remediation based on asset criticality.

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 Nettle library and how is it used?

Nettle is a low-level cryptographic library that provides developers with building blocks for secure communication, such as encryption and hashing algorithms. It is not an end-user application; rather, other software products incorporate it as a dependency to handle sensitive data security and protocol operations.

What does CVE-2023-36660 mean for memory safety?

This vulnerability is classified as CWE-787, or Out-of-bounds Write. In the context of CVE-2023-36660, the library's OCB mode implementation fails to properly manage memory during cryptographic processing. This weakness allows an attacker to overwrite adjacent memory, which can lead to system instability or the unauthorized execution of code.

How is the OCB feature flaw triggered?

The flaw requires an application using Nettle to process specific, maliciously crafted cryptographic data using the OCB mode. It is not triggered by standard operations or by simply having the library installed. Unless an application actively invokes the vulnerable OCB feature to process untrusted input, the memory corruption cannot occur.

Is my system reachable via the internet?

According to Halo Surface Signal, Nettle is a library rather than an edge service, so it is not directly reachable via the public internet. However, if an internet-facing application relies on a vulnerable version of Nettle to process incoming network traffic, that application could serve as an indirect path to the vulnerability.

What should I do if I am running software that uses Nettle?

First, identify which of your applications depend on the Nettle library. Once identified, consult with the respective application owners to determine if they utilize the affected OCB feature. Prioritize these applications based on their criticality and plan to update the library to a patched version once your software vendors provide the necessary updates.

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.