CVE-2026-59980Network attack vectorHinoki check available

Service interruption via unbounded integer decoding

Published Sep 23, 2026 · Updated Sep 23, 2026

Resource consumption in python-hyper hpack 4.1.0 and earlier allows remote attackers to interrupt service via malformed HPACK integers. The decode_integer function accepts unbounded continuation octets and repeatedly shifts and adds them into an arbitrary-precision integer, producing O(n²) work. Exploitation requires an application to pass attacker-controlled HPACK header blocks to the decoder; processing can be blocked without reported data disclosure or modification.

CVSS severity6.3
Medium
EPSS probability0.30%
Next 30 days · Oct 18, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

Resource consumption in python-hyper hpack 4.1.0 and earlier allows remote attackers to interrupt service via malformed HPACK integers. The decode_integer function accepts unbounded continuation octets and repeatedly shifts and adds them into an arbitrary-precision integer, producing O(n²) work. Exploitation requires an application to pass attacker-controlled HPACK header blocks to the decoder; processing can be blocked without reported data disclosure or modification.

The record

CVE
CVE-2026-59980
Published
Sep 23, 2026
Updated
Sep 23, 2026
Vendor
python-hyper
Product
hpack
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 23, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

python-hyper · hpackversion=< 4.2.0

Published CVSS scores

6.3GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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