DescriptionThe _encode_invalid_chars function in util/ in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
NVD severityhigh

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
python-urllib3 (PTS)stretch1.19.1-1fixed
bullseye, sid1.26.2-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
python-urllib3sourcejessie(not affected)
python-urllib3sourcestretch(not affected)
python-urllib3sourcebuster(not affected)


[buster] - python-urllib3 <not-affected> (Vulnerable code introduced later)
[stretch] - python-urllib3 <not-affected> (Vulnerable code introduced later)
[jessie] - python-urllib3 <not-affected> (Vulnerable code introduced later)
Introduced by: (1.25.2)
Fixed by: (1.25.8)

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