CVE-2026-18503: CWE-1176 in Python Software Foundation CPython
CVE-2026-18503 is a low-severity vulnerability in the Python Software Foundation's CPython implementation. It involves the csv.Sniffer.sniff() function, which can experience super-linear regular-expression processing when handling attacker-controlled CSV input. This can lead to significant CPU consumption when unbounded input is passed to this function. The vulnerability affects certain CPython versions prior to 3.16.0, including 3.14.0 and 3.15.0a1.
AI Analysis
Technical Summary
This vulnerability arises from the csv.Sniffer.sniff() method in CPython, where attacker-controlled CSV samples can cause super-linear regular-expression work during dialect sniffing. This results in excessive CPU usage when applications process unbounded input through this method. The issue is identified as CWE-1176 and affects CPython versions before 3.16.0, specifically including 3.14.0 and 3.15.0a1. The CVSS 4.0 base score is 2.4, indicating low severity. No official patch or remediation level has been provided by the vendor at this time.
Potential Impact
The vulnerability can cause significant CPU resource consumption due to super-linear regular-expression processing when untrusted CSV input is passed to csv.Sniffer.sniff(). This may degrade application performance or availability but does not indicate direct code execution or data compromise. The low CVSS score reflects limited impact confined to resource exhaustion under specific conditions.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, applications should avoid passing unbounded or untrusted CSV input to csv.Sniffer.sniff() or implement input size restrictions to mitigate potential CPU exhaustion.
CVE-2026-18503: CWE-1176 in Python Software Foundation CPython
Description
CVE-2026-18503 is a low-severity vulnerability in the Python Software Foundation's CPython implementation. It involves the csv.Sniffer.sniff() function, which can experience super-linear regular-expression processing when handling attacker-controlled CSV input. This can lead to significant CPU consumption when unbounded input is passed to this function. The vulnerability affects certain CPython versions prior to 3.16.0, including 3.14.0 and 3.15.0a1.
CVSS v4.0
Score 2.4low
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability arises from the csv.Sniffer.sniff() method in CPython, where attacker-controlled CSV samples can cause super-linear regular-expression work during dialect sniffing. This results in excessive CPU usage when applications process unbounded input through this method. The issue is identified as CWE-1176 and affects CPython versions before 3.16.0, specifically including 3.14.0 and 3.15.0a1. The CVSS 4.0 base score is 2.4, indicating low severity. No official patch or remediation level has been provided by the vendor at this time.
Potential Impact
The vulnerability can cause significant CPU resource consumption due to super-linear regular-expression processing when untrusted CSV input is passed to csv.Sniffer.sniff(). This may degrade application performance or availability but does not indicate direct code execution or data compromise. The low CVSS score reflects limited impact confined to resource exhaustion under specific conditions.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, applications should avoid passing unbounded or untrusted CSV input to csv.Sniffer.sniff() or implement input size restrictions to mitigate potential CPU exhaustion.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- PSF
- Date Reserved
- 2026-07-31T16:35:42.902Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a79dc5fbf8831d539cf709c
Added to database: 08/10/2026, 14:12:47 UTC
Last enriched: 08/10/2026, 19:32:10 UTC
Last updated: 08/10/2026, 19:32:10 UTC
Views: 6
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