Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

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

Quick assessment

Affected
python-hyper hpack
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

hpack 是用于 Python 的 HTTP/2 头编码库。在版本 4.2.0 之前，无限制的可变整数（variable integer）解码在处理畸形输入时会导致计算失控，引发 O(n²) 时间复杂度的运行性能问题，从而在输入数据足够大且未经过清洗的情况下，有效阻止后续处理。python-hyper/hpack 库的版本 4.2.0 已提供修复方案，将可变整数解码限制为 uint32 范围，以防止计算失控。作为临时缓解措施，建议在对 hpack 解码器接收到的长串 值进行输入清洗，以防范恶意利用。

CVSS 6.3 · Medium EPSS 0.30% · P23

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
python-hyper hpack < 4.2.0 affected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-59980

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
hpack: Unbounded variable integer decoding can cause run-away computation on malformed input
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
python-hyper hpack < 4.2.0 -

II. Public POCs for CVE-2026-59980

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-59980

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-59980 (2)

Vendor Advisories for CVE-2026-59980 (1)

IV. Related Vulnerabilities

Same vendor: python-hyper
Same weakness: CWE-400