stanfordnlp Stanza up to 1.14.x Lemmatizer Trainer trainer.py Trainer.load lemma_model_path deserialization

Summaryinfo

A vulnerability, which was classified as problematic, was found in stanfordnlp Stanza up to 1.14.x. This affects the function Trainer.load of the file stanza/models/lemma/trainer.py of the component Lemmatizer Trainer. The manipulation of the argument lemma_model_path results in deserialization. This vulnerability is cataloged as CVE-2026-115878. The attack must be initiated from a local position. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in stanfordnlp Stanza up to 1.14.x. Affected is the function Trainer.load of the file stanza/models/lemma/trainer.py of the component Lemmatizer Trainer. The manipulation of the argument lemma_model_path with an unknown input leads to a deserialization vulnerability. CWE is classifying the issue as CWE-502. The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Stanza is a Stanford NLP Python library for tokenization, sentence segmentation, NER, and parsing of many human languages. From 1.14.0 until 1.15.0, loading an attacker-supplied lemmatizer checkpoint can execute arbitrary code because stanza/models/lemma/trainer.py stores pos_dict as gzip-compressed pickle bytes and Trainer.load passes the decompressed stream to unrestricted pickle.loads. The outer torch.load call uses weights_only=True, but the nested bytes are treated as a primitive and are not inspected by that allowlist. The path is reachable during pipeline construction through a caller-influenced lemma_model_path, before inference begins. This issue is fixed in version 1.15.0.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-115878 since 10/23/2026. The exploitability is told to be easy. Local access is required to approach this attack. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit.

Upgrading to version 1.15.0 eliminates this vulnerability.

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Productinfo

Vendor

• stanfordnlp

Name

• Stanza

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14

Website

• Product: https://github.com/stanfordnlp/stanza/

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