llama.cpp: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-43631 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in llama.cpp from Ggml-org, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected llama.cpp versions: b7492 through b9060. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.57% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of llama.cpp you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.2 | Critical | CNA (vulncheck.com) |
| CVSS 3.1 | 8.1 | High | CNA (vulncheck.com) |
Official description
llama.cpp builds b7492 through the latest b9060 contains a use-after-free vulnerability in the vocab pointer of llama-server when the --sleep-idle-seconds feature is enabled, allowing unauthenticated remote attackers to execute arbitrary code. Attackers can trigger the vulnerability by sending requests to affected endpoints while the server transitions to sleep mode, causing concurrent worker threads to dereference a freed vocab pointer that can be reclaimed with attacker-controlled data to achieve remote code execution.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/Vladimir-tokarev-cyera/llama-cpp-security-patchesThird Party Advisory
- vulncheck.com/advisories/llama-cpp-b7492-b9060-use-after-free-rce-via-llama-serverThird Party Advisory
Other vulnerabilities in llama.cpp
- 7.5 High severity
- 8.1 High severity
- 7.8 High severity
- 8.2 High severity
- 8.1 High severity
- 7.3 High severity
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.0 High severity
- 7.4 High severity
- 7.8 High severity
- 8.8 High severity
- 7.3 High severity
- 7.0 High severity
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