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CVE-2026-82398— pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace

Quick assessment

Affected
py-pdf pypdf
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.

py-pdf pypdf是py-pdf组织开源的一款PDF文档处理组件。 pypdf 6.15.0之前版本存在资源管理错误漏洞，该漏洞源于pypdf/_utils.py中的read_until_whitespace函数在处理无空白字符的长字节流时反复进行不可变字节拼接，导致处理开销呈二次方增长，可能造成长时间运行。

CVSS 6.9 · Medium EPSS 0.52% · P44

Possible ATT&CK Techniques 1 AI

T1020.001 · Traffic Duplication

Affected Version Matrix 1

VendorProduct Version RangeStatus
py-pdf pypdf < 6.15.0 affected
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I. Basic Information for CVE-2026-82398

Vulnerability Information
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Vulnerability Title
pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace
Source: CVE Program / CVE List V5
Vulnerability Description
pypdf is a free and open-source pure-python PDF library. Prior to 6.15.0, an attacker can craft a PDF that causes long runtimes when the pypdf/_utils.py function read_until_whitespace reads a stream containing a long run of bytes without whitespace. The function repeatedly performs immutable bytes concatenation in a one-byte loop, causing quadratic processing cost for the long non-whitespace input. This issue is fixed in version 6.15.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
算法复杂性
Source: CVE Program / CVE List V5
Vulnerability Title
pypdf 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
py-pdf pypdf是py-pdf组织开源的一款PDF文档处理组件。 pypdf 6.15.0之前版本存在资源管理错误漏洞，该漏洞源于pypdf/_utils.py中的read_until_whitespace函数在处理无空白字符的长字节流时反复进行不可变字节拼接，导致处理开销呈二次方增长，可能造成长时间运行。
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
py-pdf pypdf < 6.15.0 -

II. Public POCs for CVE-2026-82398

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III. Intelligence Information for CVE-2026-82398

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Patches & Fixes for CVE-2026-82398 (1)

Vendor Advisories for CVE-2026-82398 (1)

Other References for CVE-2026-82398 (1)

IV. Related Vulnerabilities

Same product: pypdf
Same vendor: py-pdf
Same weakness: CWE-407