Remote denial of service via invalid typecodes
Published Sep 10, 2021 · Updated Aug 4, 2024
Denial of service in rencode 1.0.6 and earlier allows remote attackers to hang Python processes via malformed encoded input. The Cython decode function returns without advancing the input position for an invalid typecode inside a list or dictionary, so the enclosing terminator loop never exits. Any network-facing application that passes attacker-controlled bytes to rencode.loads can lock its interpreter while consuming CPU and memory.
Summary
What happened
Denial of service in rencode 1.0.6 and earlier allows remote attackers to hang Python processes via malformed encoded input. The Cython decode function returns without advancing the input position for an invalid typecode inside a list or dictionary, so the enclosing terminator loop never exits. Any network-facing application that passes attacker-controlled bytes to rencode.loads can lock its interpreter while consuming CPU and memory.
The record
- CVE
- CVE-2021-40839
- Published
- Sep 10, 2021
- Updated
- Aug 4, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-835, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 10, 2021CVE publishedPublication date reported by the CVE source.
- Aug 4, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- rencode 3-byte packet DoSproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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