High [CVE-2026-43632] Potential code execution via a race condition in tokenization endpoints
This high-severity Red Hat Linux advisory covers CVE-2026-43632.
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Summary
llama.cpp builds b7492 through the latest b9060 contains a use-after-free vulnerability in llama-server affecting six tokenization endpoints (/tokenize, /detokenize, /infill, /apply-template, /rerank, and /anthropic/count_tokens) that bypass the task queue and access ctx_server.vocab directly on HTTP worker threads.
Attackers can exploit a time-of-check-time-of-use race condition where the main thread destroys and frees vocab after the synchronization lock is released but before the handler finishes using it, causing a crash or potential code execution when --sleep-idle-seconds is configured.
Successful exploitation could lead to a system crash or potentially arbitrary code execution. This occurs when the main thread releases synchronization locks and destroys the vocabulary structure while an HTTP worker thread is still actively processing a request.
An unauthenticated remote attacker sending concurrent HTTP requests can trigger heap corruption, leading to a service crash (Denial of Service) or potential arbitrary code execution within the security context of the llama-server process.
Because exploitation relies on tight timing windows during idle cleanup cycles and impact is contained within the process boundaries without inherent host privilege escalation or OS isolation bypass, this vulnerability has been rated with an Important severity.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- To mitigate this issue, avoid configuring the `llama-server` with the `--sleep-idle-seconds` option. Disabling this option prevents the specific race condition that leads to the use-after-free vulnerability. If `llama-server` is running as a service, a restart of the service will be required for the change to take effect.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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