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CVE-2026-18503— Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()

Quick assessment

Affected
Python Software Foundation CPython
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.

Python Software Foundation CPython是Python Software Foundation基金会的一款编程语言解释器。 Python Software Foundation CPython 3.13.15之前版本、3.14.0至3.14.7之前版本和3.15.0a1至3.15.0rc1之前版本存在资源管理错误漏洞，该漏洞源于csv.Sniffer.sniff()函数在处理无界输入时触发超线性正则表达式工作，可能导致CPU资源消耗。

CVSS 2.4 · Low EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 6

VendorProduct Version RangeStatus
Python Software Foundation CPython < 3.10.21 affected
3.11.0< 3.11.16 affected
3.12.0< 3.12.14 affected
3.13.0< 3.13.15 affected
3.14.0< 3.14.7 affected
3.15.0a1< 3.15.0rc1 affected
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I. Basic Information for CVE-2026-18503

Vulnerability Information
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Vulnerability Title
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
Source: CVE Program / CVE List V5
Vulnerability Description
Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and consume significant CPU when applications pass unbounded input to csv.Sniffer.sniff().
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
低效的CPU计算
Source: CVE Program / CVE List V5
Vulnerability Title
Python Software Foundation CPython 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Python Software Foundation CPython是Python Software Foundation基金会的一款编程语言解释器。 Python Software Foundation CPython 3.13.15之前版本、3.14.0至3.14.7之前版本和3.15.0a1至3.15.0rc1之前版本存在资源管理错误漏洞，该漏洞源于csv.Sniffer.sniff()函数在处理无界输入时触发超线性正则表达式工作，可能导致CPU资源消耗。
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
Python Software Foundation CPython 0 ~ 3.10.21 -

II. Public POCs for CVE-2026-18503

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III. Intelligence Information for CVE-2026-18503

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Patches & Fixes for CVE-2026-18503 (6)

Vendor Advisories for CVE-2026-18503 (1)

Mailing List Discussions for CVE-2026-18503 (1)

IV. Related Vulnerabilities

Same product: CPython
Same vendor: Python Software Foundation

V. Comments for CVE-2026-18503

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