CVE-2026-52132
Description
A flaw was found in llama.cpp. A remote attacker can exploit this vulnerability when the application is started with the --reranking flag. By sending a POST request to the /rerank endpoint with a negative top_n value, the attacker can cause a std::bad_alloc error and an HTTP 500 response, leading to a Denial of Service (DoS).
Statement
A flaw was found in llama.cpp when running in server mode with reranking enabled. An unauthenticated remote attacker can issue a POST request to the /rerank endpoint containing a negative top_n parameter value. This invalid input triggers an uncontrolled memory allocation attempt (std::bad_alloc), leading to an application exception or process crash that results in a denial of service.
Mitigation
Disable the --reranking command-line flag if reranking capabilities are not required. If reranking functionality must remain enabled, configure an upstream reverse proxy or API gateway to validate POST request payloads to /rerank and block requests containing negative top_n values.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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