CVE-2026-18503
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
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().
INFO
Published Date :
Aug. 10, 2026, 2:17 p.m.
Last Modified :
Aug. 10, 2026, 6:17 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-18503
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | LOW | 28c92f92-d60d-412d-b760-e73465c3df22 | ||||
| CVSS 4.0 | LOW | [email protected] |
Solution
- Limit input size for csv.Sniffer.sniff().
- Validate CSV data before processing.
- Update to a version with improved parsing limits.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-18503.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-18503 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-18503
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-18503 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-18503 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 10, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-18503', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-10T17:56:17.853221Z'} -
CVE Modified by [email protected]
Aug. 10, 2026
Action Type Old Value New Value Added Reference https://github.com/python/cpython/commit/063d4555c94ef412c731527dbf30193327f2ee82 Added Reference https://github.com/python/cpython/commit/476fb09cdb0d73e645849d98c610e7e5697ce7c9 Added Reference https://github.com/python/cpython/commit/89f29c760c02774b099ddd6863268eb13fa3946a Added Reference https://github.com/python/cpython/commit/b30c7fa9edd921a118f286e9f90f560777fa693b Changed Affected [{'repo': 'https://github.com/python/cpython', 'vendor': 'Python Software Foundation', 'modules': ['csv'], 'product': 'CPython', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.16.0', 'versionType': 'python'}], 'defaultStatus': 'unaffected'}] [{'repo': 'https://github.com/python/cpython', 'vendor': 'Python Software Foundation', 'modules': ['csv'], 'product': 'CPython', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.13.15', 'versionType': 'python'}, {'status': 'affected', 'version': '3.14.0', 'lessThan': '3.14.7', 'versionType': 'python'}, {'status': 'affected', 'version': '3.15.0a1', 'lessThan': '3.15.0rc1', 'versionType': 'python'}], 'defaultStatus': 'unaffected'}] -
New CVE Received by [email protected]
Aug. 10, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/python/cpython', 'vendor': 'Python Software Foundation', 'modules': ['csv'], 'product': 'CPython', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '3.16.0', 'versionType': 'python'}], 'defaultStatus': 'unaffected'}] Added 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(). Added CVSS V4.0 AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-1176 Added Reference https://github.com/python/cpython/issues/98820 Added Reference https://github.com/python/cpython/pull/153694 Added Reference https://mail.python.org/archives/list/[email protected]/thread/KQ7NBMCPAZJHRROQXJQE4GMXGLD5KHBS/