Is CVE-2026-52131 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-52131 being exploited in the wild.

How severe is CVE-2026-52131?

High severity, with a CVSS score of 7.5, published 1 September 2026.

Which products and versions are affected?

ggml-org llama.cpp b5693 and before.

Is there a fix for CVE-2026-52131?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-52131 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-52131?

Check whether you run GGML Llama.Cpp. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-52131: llama.cpp uncontrolled recursion denial of service in json-schema-to-grammar

CVE-2026-52131 · Severity: high · CVSS 7.5 · Published 2026-09-01

llama.cpp is an inference engine for large language models used in AI applications. A flaw in its JSON schema grammar conversion allows attackers to crash the server by submitting deeply nested JSON schema payloads, causing service disruption. The vulnerability affects only the /completions API endpoint and requires no authentication.

Technologies: GGML Llama.Cpp. Vendors: GGML.

Quick answers

Is CVE-2026-52131 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-52131 being exploited in the wild.
How severe is CVE-2026-52131?: High severity, with a CVSS score of 7.5, published 1 September 2026.
Which products and versions are affected?: ggml-org llama.cpp b5693 and before.
Is there a fix for CVE-2026-52131?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-52131 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-52131?: Check whether you run GGML Llama.Cpp. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is an uncontrolled recursion (CWE-674) in the SchemaConverter::visit and _generate_union_rule functions within common/json-schema-to-grammar.cpp. When processing deeply nested JSON schemas (recursion depth ≥ 7000) submitted via the POST /completions endpoint's json_schema field, the recursion exhausts the thread stack and crashes the server. No recursion depth limits are enforced in the vulnerable functions. The vulnerability is network-reachable without authentication, and proof-of-concept reproduction is confirmed at depths ≥7000 on x86-64 Linux with default 8 MB thread stacks. As of the latest release (b10405 / 2026-08-13), the vulnerability remains unpatched.

Affected products

ggml-org llama.cpp b5693 and before

Timeline

2026-08-12: disclosed
2026-09-01: advisory

References

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