Denial of service via unbounded tag identifiers
Published Jul 14, 2026 · Updated Jul 14, 2026
Uncontrolled resource consumption in pyasn1 before 0.6.4 allows remote attackers to interrupt services via crafted ASN.1 input. The shared BER decoder accumulates continuation octets into a long-form tag identifier without a bound, creating arbitrarily large integers with quadratic CPU cost and exposing error formatting to unhandled ValueError exceptions. Reachability requires an application to decode attacker-controlled BER, CER, or DER data; affected processes can stall or exit outside callers that handle only PyAsn1Error.
Summary
What happened
Uncontrolled resource consumption in pyasn1 before 0.6.4 allows remote attackers to interrupt services via crafted ASN.1 input. The shared BER decoder accumulates continuation octets into a long-form tag identifier without a bound, creating arbitrarily large integers with quadratic CPU cost and exposing error formatting to unhandled ValueError exceptions. Reachability requires an application to decode attacker-controlled BER, CER, or DER data; affected processes can stall or exit outside callers that handle only PyAsn1Error.
The record
- CVE
- CVE-2026-59884
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Vendor
- pyasn1
- Product
- pyasn1
- Classifications
- CWE-400, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 14, 2026CVE publishedPublication date reported by the CVE source.
- Jul 14, 2026Record 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=< 0.6.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
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Technologies
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Your stack
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