Python CPython Unicode unicodedata.normalize algorithmic complexity

CVSS Meta Temp Score
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CTI Interest Score
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5.3$0-$5k3.86-

Summaryinfo

A vulnerability classified as problematic has been found in Python CPython. The affected element is the function unicodedata.normalize of the component Unicode Handler. This manipulation causes algorithmic complexity. This vulnerability appears as CVE-2026-3276. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in Python CPython (version now known). It has been declared as problematic. Affected by this vulnerability is the function unicodedata.normalize of the component Unicode Handler. The manipulation with an unknown input leads to a algorithmic complexity vulnerability. The CWE definition for the vulnerability is CWE-407. An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached. As an impact it is known to affect availability. The summary by CVE is:

unicodedata.normalize() can take excessive CPU time when processing specially crafted Unicode input containing long runs of combining characters with alternating Canonical Combining Class values. This affects all normalization forms.

It is possible to read the advisory at mail.python.org. This vulnerability is known as CVE-2026-3276 since 02/26/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

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Vendor

Name

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.3

VulDB Base Score: 5.3
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Algorithmic complexity
CWE: CWE-407 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

02/26/2026 CVE reserved
06/03/2026 +96 days Advisory disclosed
06/03/2026 +0 days VulDB entry created
06/03/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: mail.python.org
Status: Confirmed

CVE: CVE-2026-3276 (🔒)
GCVE (CVE): GCVE-0-2026-3276
GCVE (VulDB): GCVE-100-368143

Entryinfo

Created: 06/03/2026 18:14
Changes: 06/03/2026 18:14 (66)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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