hpack: Unbounded variable integer decoding can cause run-away computation on malformed input
cve-program · CVE-2026-59980
Publishedhpack 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.
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cve-program · CVE-2026-59980
Publishedhpack: Unbounded variable integer decoding can cause run-away computation on malformed input
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.
- Source published
- 23 Sep 2026 22:07:35 UTC
- Source modified
- 24 Sep 2026 13:25:08 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
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- CVE Program Terms of Use
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CVSS 4.0 · 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N