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CVE-2026-18503VulnerabilityPublished Updated

Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and consume

Source GCVE Database

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Authoritative record:CVE-2026-18503· Low 2.4

Not known to be exploited · CVSS 2.4 Low · fixed in 3.16.0 : update CPython when convenient.

Data as of 10 Nov 2026, 16:36 UTC

CVSS 4.0 base score
2.4Low
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (PSF)CVSS 4.02.4
Patch
Available – fixed in 3.16.0, 3.15.0rc1, 3.14.7 +4
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Python Software FoundationCPythonAffected
  • >=3.16.0a1 <3.16.0
Fixed in
  • 3.16.0
Python Software FoundationCPythonAffected
  • >=3.15.0a1 <3.15.0rc1
Fixed in
  • 3.15.0rc1
Python Software FoundationCPythonAffected
  • >=3.14.0 <3.14.7
Fixed in
  • 3.14.7
Python Software FoundationCPythonAffected
  • >=3.13.0 <3.13.15
Fixed in
  • 3.13.15
Python Software FoundationCPythonAffected
  • >=3.12.0 <3.12.14
Fixed in
  • 3.12.14
Python Software FoundationCPythonAffected
  • >=3.11.0 <3.11.16
Fixed in
  • 3.11.16

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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().

References

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