# CVE-2026-27940: llama.cpp has a Heap Buffer Overflow via Integer Overflow in `mem_size` Calculation — Bypass of CVE-2025-53630 Fix

> An integer overflow in llama.cpp allows heap buffer overflows via crafted GGUF files, potentially enabling code execution or crashes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 12 Mar 2026
- **Updated:** 14 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-27940, GHSA-3p4r-fq3f-q74v, UBUNTU-CVE-2026-27940

## What is CVE-2026-27940?

CVE-2026-27940 is a high-severity vulnerability in ggml-org llama.cpp, published on 12 Mar 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

llama.cpp is an inference of several LLM models in C/C++. Prior to b8146, the gguf_init_from_file_impl() in gguf.cpp is vulnerable to an Integer overflow, leading to an undersized heap allocation. Using the subsequent fread() writes 528+ bytes of attacker-controlled data past the buffer boundary. This is a bypass of a similar bug in the same file - CVE-2025-53630, but the fix overlooked some areas. This vulnerability is fixed in b8146.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-27940?

It affects 1 product.


Products: Ggml Llama.cpp.

## How do I fix CVE-2026-27940?

Upgrade to a fixed version.

## Is CVE-2026-27940 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27940 exists.

Public exploit code:

- https://github.com/ngtuonghung/CVE-2026-27940 (github_poc): https://github.com/ngtuonghung/CVE-2026-27940

## Other vulnerabilities in ggml-org llama.cpp

- [CVE-2024-42479](https://insights.sbomify.com/CVE-2024-42479/): llama.cpp allows write-what-where in rpc_server::set_tensor (critical 10.0)
- [CVE-2026-34159](https://insights.sbomify.com/CVE-2026-34159/): llama.cpp: Unauthenticated RCE via GRAPH_COMPUTE buffer=0 bypass in llama.cpp RPC backend (critical 9.8)
- [CVE-2026-43629](https://insights.sbomify.com/CVE-2026-43629/): llama.cpp b4882–b9058 Buffer Overflow in KV Cache State Restore (critical 9.2)
- [CVE-2026-43631](https://insights.sbomify.com/CVE-2026-43631/): llama.cpp b7492–b9060 Use-After-Free RCE via llama-server (critical 9.2)
- [CVE-2026-43632](https://insights.sbomify.com/CVE-2026-43632/): llama.cpp b7492–b9060 Use-After-Free in Tokenization Endpoints (critical 9.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27940 and fix it if it is affected.

What it is: CVE-2026-27940 is a high-severity vulnerability in ggml-org llama.cpp, published on 12 Mar 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27940 exists.

Affected product: ggml-org llama.cpp. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27940/ (Markdown: https://insights.sbomify.com/CVE-2026-27940/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27940
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27940
- OSV: https://osv.dev/vulnerability/CVE-2026-27940

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27940/
Summaries are generated and may contain mistakes; the official description above is the record.