# CVE-2026-52132: llama.cpp denial of service via negative top_n in reranking API

Source: https://junglewise.ai/threats/cve-2026-52132-llama-cpp-denial-of-service-via-negative-top-n-in-reranking-api  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-01. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-52132 · Severity: high · CVSS 7.5 · Published 2026-09-01

llama.cpp is a C++ framework for running large language model inference. When started with the --reranking flag to enable document reranking functionality, the API fails to validate input parameters and crashes on malformed requests. A remote attacker can send a specially crafted POST request with a negative "top_n" value to cause the service to return HTTP 500 errors and exhaust memory, making the inference service unavailable to legitimate users.

Technologies: [GGML Llama.Cpp](https://junglewise.ai/threats/technologies/llama-cpp). Vendors: [GGML](https://junglewise.ai/threats/vendors/ggml).

## Quick answers

**Is CVE-2026-52132 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-52132 being exploited in the wild.

**How severe is CVE-2026-52132?** High severity, with a CVSS score of 7.5, published 1 September 2026.

**Which products and versions are affected?** GGML Llama.Cpp through commit 97f06e9.

**Is there a fix for CVE-2026-52132?** 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-2026-52132 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-52132?** Check whether you run GGML Llama.Cpp at an affected version. 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 integer handling error (CWE-190) in the /rerank endpoint handler, specifically in tools/server/server-context.cpp (line 4048) where the top_n parameter is extracted from the JSON request body without validation. When a negative top_n value is passed, it triggers a std::bad_alloc exception in the memory allocation routines of format_response_rerank (tools/server/server-common.cpp, line 1245), causing the server to return HTTP 500 errors. The attack requires the server to be explicitly started with the --reranking flag (not enabled by default) and network access to the HTTP API endpoint. The vulnerability is 100% reproducible with negative top_n values and causes denial of service through repeated crashes, though the server process survives individual incidents. No patch has been released as of the latest stable version.

## Affected products

- ggml llama.cpp through commit 97f06e9

## Timeline

- 2026-08-12: disclosed
- 2026-09-01: advisory: Published to NVD

## References

- [https://blog.ph4nt0m.xyz/ko/cves/cve-2026-52132/](https://blog.ph4nt0m.xyz/ko/cves/cve-2026-52132/)
- [https://github.com/ggml-org/llama.cpp](https://github.com/ggml-org/llama.cpp)

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- [llama.cpp builds b1886 through b7445 contain a race condition use-after-free vulnerability in the LLaMA-Android JNI…](https://junglewise.ai/threats/cve-2026-70640-llama-cpp-builds-b1886-through-b7445-contain-a-race-condition-use)
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