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CVE-2026-85670— tokenizers BpeBuilder Buffer Overflow via merge token

Quick assessment

Affected
huggingface tokenizers
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Hugging Face Tokenizers是Hugging Face公司的一个将文本切分为词元的高性能工具。 Hugging Face Tokenizers 0.23.2及之前版本存在缓冲区错误漏洞，该漏洞源于tokenizers/src/models/bpe/model.rs中的BpeBuilder::build存在越界缓冲区访问，加载特制的tokenizer.json时，合并规则超过最长词汇键可能导致缓冲区溢出，造成拒绝服务，特定配置下还可能发生usize下溢，导致内存损坏。

CVSS 6.5 · Medium EPSS 0.31% · P24

Possible ATT&CK Techniques 1 AI

T1201 · Password Policy Discovery

Affected Version Matrix 1

VendorProduct Version RangeStatus
huggingface tokenizers ≤ 0.23.2 affected
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I. Basic Information for CVE-2026-85670

Vulnerability Information
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Vulnerability Title
tokenizers BpeBuilder Buffer Overflow via merge token
Source: CVE Program / CVE List V5
Vulnerability Description
tokenizers (Hugging Face) is affected by an out-of-bounds buffer access in BpeBuilder::build (tokenizers/src/models/bpe/model.rs). When loading a tokenizer.json via Tokenizer::from_file/from_str, the builder sizes a scratch buffer to the longest vocabulary key, then writes each concatenated merge rule into it. A merge whose concatenated token exceeds the longest vocabulary key overruns the buffer, which Rust turns into a panic that aborts the process in Rust and FFI embeddings. This occurs at load time with no encoding required, so an attacker who supplies a crafted tokenizer.json can cause a denial of service. A secondary defect at the same location can cause a usize underflow (panic in debug, potential memory corruption in release) when continuing_subword_prefix is set and a merge token is shorter than the prefix. Observed in version 0.23.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
Hugging Face Tokenizers 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Hugging Face Tokenizers是Hugging Face公司的一个将文本切分为词元的高性能工具。 Hugging Face Tokenizers 0.23.2及之前版本存在缓冲区错误漏洞，该漏洞源于tokenizers/src/models/bpe/model.rs中的BpeBuilder::build存在越界缓冲区访问，加载特制的tokenizer.json时，合并规则超过最长词汇键可能导致缓冲区溢出，造成拒绝服务，特定配置下还可能发生usize下溢，导致内存损坏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
huggingface tokenizers 0 ~ 0.23.2 -

II. Public POCs for CVE-2026-85670

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III. Intelligence Information for CVE-2026-85670

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Vendor Advisories for CVE-2026-85670 (1)

Mailing List Discussions for CVE-2026-85670 (1)

IV. Related Vulnerabilities

Same vendor: huggingface
Same weakness: CWE-787

V. Comments for CVE-2026-85670

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