Service interruption via unbounded integer conversions
Published Sep 9, 2022 · Updated Nov 3, 2025
Algorithmic complexity in CPython 3.7 allows remote attackers to interrupt services through oversized decimal integer strings. PyLong_FromString and related integer-to-string paths perform near-quadratic work on non-power-of-two bases without bounding digit counts, so int() on attacker-controlled decimal text can consume excessive CPU. Exploitation requires a network-facing application to pass attacker-controlled text to these conversions; the bounded consequence is a stalled or unavailable application process.
Summary
What happened
Algorithmic complexity in CPython 3.7 allows remote attackers to interrupt services through oversized decimal integer strings. PyLong_FromString and related integer-to-string paths perform near-quadratic work on non-power-of-two bases without bounding digit counts, so int() on attacker-controlled decimal text can consume excessive CPU. Exploitation requires a network-facing application to pass attacker-controlled text to these conversions; the bounded consequence is a stalled or unavailable application process.
The record
- CVE
- CVE-2020-10735
- Published
- Sep 9, 2022
- Updated
- Nov 3, 2025
- Vendor
- Python Software Foundation
- Product
- CPython
- Classifications
- CWE-770, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 9, 2022CVE publishedPublication date reported by the CVE source.
- Nov 3, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=python 3.7
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
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Public exploit references
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Your stack
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