CVE-2026-1839 Arbitrary Code Execution via Unsafe torch.load() in Trainer Checkpoint Loading in huggingface/transformers
Attackers can execute arbitrary code by supplying malicious checkpoint files to the Trainer class due to unsafe deserialization in torch.load.
- 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
What is CVE-2026-1839?
CVE-2026-1839 is a medium-severity unsafe deserialization vulnerability in huggingface/transformers, published on 7 Apr 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
A vulnerability in the HuggingFace Transformers library, specifically in the `Trainer` class, allows for arbitrary code execution. The `_load_rng_state()` method in `src/transformers/trainer.py` at line 3059 calls `torch.load()` without the `weights_only=True` parameter. This issue affects all versions of the library supporting `torch>=2.2` when used with PyTorch versions below 2.6, as the `safe_globals()` context manager provides no protection in these versions. An attacker can exploit this vulnerability by supplying a malicious checkpoint file, such as `rng_state.pth`, which can execute arbitrary code when loaded. The issue is resolved in version v5.0.0rc3.
Weakness: CWE-502
Which versions are affected by CVE-2026-1839?
3 open source packages ship an affected version, including transformers. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
transformers PyPI | All versions | 5.0.0 |
transformers PyPI | All versions | 5.0.0rc3 |
transformers PyPI | All versions | 5.0.0rc3 |
Products include Huggingface Transformers.
How do I fix CVE-2026-1839?
Upgrade transformers to a fixed version for your release line: 5.0.0 or 5.0.0rc3.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-1839 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-1839 exists.
Other vulnerabilities in huggingface/transformers
- CVE-2023-7018 Deserialization of Untrusted Data in huggingface/transformers
- CVE-2023-6730 Deserialization of Untrusted Data in huggingface/transformers
- CVE-2024-11393 Hugging Face Transformers MaskFormer Model Deserialization of Untrusted Data Remote Code Execution Vulnerability
- CVE-2024-11394 Hugging Face Transformers Trax Model Deserialization of Untrusted Data Remote Code Execution Vulnerability
- CVE-2026-5241 Policy Bypass in LightGlue Nested Config Resolution in huggingface/transformers
Sources
Also known as CLSA-2026-1779065183, ECHO-9bd3-047a-4b4a, GHSA-69w3-r845-3855, PYSEC-2026-2288.