#VU68608 Incorrect Regular Expression in Pillow - CVE-2021-23437

Vulnerability identifier: #VU68608

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-23437

CWE-ID: CWE-185

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Pillow
Universal components / Libraries / Libraries used by multiple products

Vendor: Alex Clark and Contributors

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient input validation when processing regular expressions. A remote attacker can pass specially crafted data to the application and perform regular expression denial of service (ReDos) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Pillow: 5.2.0 - 8.3.1

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External links
https://pillow.readthedocs.io/en/stable/releasenotes/8.3.2.html
https://github.com/python-pillow/Pillow/commit/9e08eb8f78fdfd2f476e1b20b7cf38683754866b
https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1319443
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VKRCL7KKAKOXCVD7M6WC5OKFGL4L3SJT/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RNSG6VFXTAROGF7ACYLMAZNQV4EJ6I2C/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.