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Vulnerability record · CVE-2021-40839 · published 10 September 2021

CVE-2021-40839: Rencode project rencode vulnerability

Rencode Project · Rencode

The rencode package through 1.0.6 for Python allows an infinite loop in typecode decoding (such as via ;\x2f\x7f), enabling a remote attack that consumes CPU and memory.

7.5 CVSS 3.1 High EPSS 5.6% · top 7.4% CWE-835 · CWE-835
7.5CVSS 3.1 base score, v2 5.0
5.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
14References
17 Jun 2026Last modified by NVD

Description

The rencode package through 1.0.6 for Python allows an infinite loop in typecode decoding (such as via ;\x2f\x7f), enabling a remote attack that consumes CPU and memory.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/aresch/rencode/commit/572ff74586d9b1daab904c6f7f7009ce0143bb75 PatchThird Party Advisory
https://github.com/aresch/rencode/pull/29 PatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMVQRPDVSVZNGGX57CFKCYT
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MCLETLGVM5DBX6QNHQFW6TW
https://pypi.org/project/rencode/#history Third Party Advisory
https://seclists.org/fulldisclosure/2021/Sep/16 Mailing ListThird Party Advisory
https://security.netapp.com/advisory/ntap-20211008-0001/ Third Party Advisory
https://github.com/aresch/rencode/commit/572ff74586d9b1daab904c6f7f7009ce0143bb75 PatchThird Party Advisory
https://github.com/aresch/rencode/pull/29 PatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BMVQRPDVSVZNGGX57CFKCYT
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MCLETLGVM5DBX6QNHQFW6TW
https://pypi.org/project/rencode/#history Third Party Advisory
https://seclists.org/fulldisclosure/2021/Sep/16 Mailing ListThird Party Advisory
https://security.netapp.com/advisory/ntap-20211008-0001/ Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-40839), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.