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CVE-2026-59980 - hpack: Unbounded variable integer decoding can cause run-away computation on malformed input

CVE ID :CVE-2026-59980
Published : Sept. 23, 2026, 11:17 p.m. | 1 hour, 53 minutes ago
Description :hpack is an HTTP/2 Header Encoding for Python. Prior to version 4.2.0, unbounded variable integer decoding can cause run-away computation on malformed input leading to O(n^2) runtime, effectively blocking further processing with large enough unsanitized input. A fix is available in python-hyper/hpack v4.2.0 to restricted variable integer decoding to uint32 to prevent run-away computation. As a workaround, sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.
Severity: 6.3 | MEDIUM
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