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CVE-2026-62239— FlashAttention Symlink Attack via tarfile.extractall in hopper/setup.py

Quick assessment

Affected
Dao-AILab flash-attention
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.

Dao AI Lab FlashAttention是Dao AI Lab团队开源的一个高效且节省内存的注意力机制实现工具。 Dao AI Lab FlashAttention 2.8.3.post1及之前版本存在后置链接漏洞，该漏洞源于hopper/setup.py中的download_and_copy()函数在提取NVIDIA toolchain归档时未验证symlink或过滤tar成员，本地攻击者可在可预测缓存目录中预置symlink，将提取的二进制文件重定向到攻击者选择的位置，从而在构建期间以受害者

CVSS 6.6 · Medium EPSS 0.16% · P5

Affected Version Matrix 2

VendorProduct Version RangeStatus
Dao-AILab flash-attention ≤ 2.8.3.post1 affected
0816ef12f424c6ec94b057a72c275b14f6e6edb2 unaffected
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I. Basic Information for CVE-2026-62239

Vulnerability Information
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Vulnerability Title
FlashAttention Symlink Attack via tarfile.extractall in hopper/setup.py
Source: CVE Program / CVE List V5
Vulnerability Description
FlashAttention through 2.8.3.post1, fixed in commit 0816ef1, contains a symlink attack vulnerability in the download_and_copy() function within hopper/setup.py that extracts NVIDIA toolchain archives without validating symlinks or filtering tar members. A local attacker can pre-plant a symlink in the predictable cache directory to redirect extracted binaries to an attacker-chosen location, enabling arbitrary file write with victim privileges during build time.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在文件访问前对链接解析不恰当(链接跟随)
Source: CVE Program / CVE List V5
Vulnerability Title
Dao AI Lab FlashAttention 后置链接漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Dao AI Lab FlashAttention是Dao AI Lab团队开源的一个高效且节省内存的注意力机制实现工具。 Dao AI Lab FlashAttention 2.8.3.post1及之前版本存在后置链接漏洞，该漏洞源于hopper/setup.py中的download_and_copy()函数在提取NVIDIA toolchain归档时未验证symlink或过滤tar成员，本地攻击者可在可预测缓存目录中预置symlink，将提取的二进制文件重定向到攻击者选择的位置，从而在构建期间以受害者
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
Dao-AILab flash-attention 0 ~ 2.8.3.post1 -

II. Public POCs for CVE-2026-62239

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III. Intelligence Information for CVE-2026-62239

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Patches & Fixes for CVE-2026-62239 (2)

Vendor Advisories for CVE-2026-62239 (1)

Proof of Concept for CVE-2026-62239 (1)

IV. Related Vulnerabilities

Same weakness: CWE-59

V. Comments for CVE-2026-62239

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