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Vulnerability details: VCID-v365-pn8r-e7dh
Vulnerability ID VCID-v365-pn8r-e7dh
Aliases CVE-2025-66418
GHSA-gm62-xv2j-4w53
Summary urllib3 allows an unbounded number of links in the decompression chain urllib3 supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., `Content-Encoding: gzip, zstd`). However, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (3)
System Score Found at
cvssv3 7.5 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2025-66418.json
epss 0.00029 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00029 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
epss 0.00033 https://api.first.org/data/v1/epss?cve=CVE-2025-66418
cvssv3.1 5.3 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv3.1_qr HIGH https://github.com/advisories/GHSA-gm62-xv2j-4w53
cvssv4 8.9 https://github.com/urllib3/urllib3
generic_textual HIGH https://github.com/urllib3/urllib3
cvssv4 8.9 https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
generic_textual HIGH https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
ssvc Track https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
cvssv3.1_qr HIGH https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
cvssv4 8.9 https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
generic_textual HIGH https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
ssvc Track https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
cvssv4 8.9 https://nvd.nist.gov/vuln/detail/CVE-2025-66418
generic_textual HIGH https://nvd.nist.gov/vuln/detail/CVE-2025-66418
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2025-66418.json
https://api.first.org/data/v1/epss?cve=CVE-2025-66418
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-66418
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://github.com/urllib3/urllib3
https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
1122030 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1122030
2419455 https://bugzilla.redhat.com/show_bug.cgi?id=2419455
CVE-2025-66418 https://nvd.nist.gov/vuln/detail/CVE-2025-66418
GHSA-gm62-xv2j-4w53 https://github.com/advisories/GHSA-gm62-xv2j-4w53
GHSA-gm62-xv2j-4w53 https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
RHSA-2026:0050 https://access.redhat.com/errata/RHSA-2026:0050
RHSA-2026:0414 https://access.redhat.com/errata/RHSA-2026:0414
RHSA-2026:0990 https://access.redhat.com/errata/RHSA-2026:0990
RHSA-2026:10184 https://access.redhat.com/errata/RHSA-2026:10184
RHSA-2026:1026 https://access.redhat.com/errata/RHSA-2026:1026
RHSA-2026:1027 https://access.redhat.com/errata/RHSA-2026:1027
RHSA-2026:1041 https://access.redhat.com/errata/RHSA-2026:1041
RHSA-2026:1042 https://access.redhat.com/errata/RHSA-2026:1042
RHSA-2026:1086 https://access.redhat.com/errata/RHSA-2026:1086
RHSA-2026:1087 https://access.redhat.com/errata/RHSA-2026:1087
RHSA-2026:1088 https://access.redhat.com/errata/RHSA-2026:1088
RHSA-2026:1089 https://access.redhat.com/errata/RHSA-2026:1089
RHSA-2026:1168 https://access.redhat.com/errata/RHSA-2026:1168
RHSA-2026:1176 https://access.redhat.com/errata/RHSA-2026:1176
RHSA-2026:1224 https://access.redhat.com/errata/RHSA-2026:1224
RHSA-2026:1226 https://access.redhat.com/errata/RHSA-2026:1226
RHSA-2026:1239 https://access.redhat.com/errata/RHSA-2026:1239
RHSA-2026:1240 https://access.redhat.com/errata/RHSA-2026:1240
RHSA-2026:1241 https://access.redhat.com/errata/RHSA-2026:1241
RHSA-2026:1254 https://access.redhat.com/errata/RHSA-2026:1254
RHSA-2026:1329 https://access.redhat.com/errata/RHSA-2026:1329
RHSA-2026:1330 https://access.redhat.com/errata/RHSA-2026:1330
RHSA-2026:1331 https://access.redhat.com/errata/RHSA-2026:1331
RHSA-2026:1332 https://access.redhat.com/errata/RHSA-2026:1332
RHSA-2026:1336 https://access.redhat.com/errata/RHSA-2026:1336
RHSA-2026:1337 https://access.redhat.com/errata/RHSA-2026:1337
RHSA-2026:1338 https://access.redhat.com/errata/RHSA-2026:1338
RHSA-2026:1339 https://access.redhat.com/errata/RHSA-2026:1339
RHSA-2026:1340 https://access.redhat.com/errata/RHSA-2026:1340
RHSA-2026:1485 https://access.redhat.com/errata/RHSA-2026:1485
RHSA-2026:1504 https://access.redhat.com/errata/RHSA-2026:1504
RHSA-2026:1546 https://access.redhat.com/errata/RHSA-2026:1546
RHSA-2026:1618 https://access.redhat.com/errata/RHSA-2026:1618
RHSA-2026:1619 https://access.redhat.com/errata/RHSA-2026:1619
RHSA-2026:1652 https://access.redhat.com/errata/RHSA-2026:1652
RHSA-2026:1674 https://access.redhat.com/errata/RHSA-2026:1674
RHSA-2026:1676 https://access.redhat.com/errata/RHSA-2026:1676
RHSA-2026:1693 https://access.redhat.com/errata/RHSA-2026:1693
RHSA-2026:1701 https://access.redhat.com/errata/RHSA-2026:1701
RHSA-2026:1702 https://access.redhat.com/errata/RHSA-2026:1702
RHSA-2026:1704 https://access.redhat.com/errata/RHSA-2026:1704
RHSA-2026:1712 https://access.redhat.com/errata/RHSA-2026:1712
RHSA-2026:1726 https://access.redhat.com/errata/RHSA-2026:1726
RHSA-2026:1729 https://access.redhat.com/errata/RHSA-2026:1729
RHSA-2026:1730 https://access.redhat.com/errata/RHSA-2026:1730
RHSA-2026:1736 https://access.redhat.com/errata/RHSA-2026:1736
RHSA-2026:1942 https://access.redhat.com/errata/RHSA-2026:1942
RHSA-2026:1957 https://access.redhat.com/errata/RHSA-2026:1957
RHSA-2026:2106 https://access.redhat.com/errata/RHSA-2026:2106
RHSA-2026:2126 https://access.redhat.com/errata/RHSA-2026:2126
RHSA-2026:2137 https://access.redhat.com/errata/RHSA-2026:2137
RHSA-2026:2139 https://access.redhat.com/errata/RHSA-2026:2139
RHSA-2026:2144 https://access.redhat.com/errata/RHSA-2026:2144
RHSA-2026:2256 https://access.redhat.com/errata/RHSA-2026:2256
RHSA-2026:2279 https://access.redhat.com/errata/RHSA-2026:2279
RHSA-2026:2456 https://access.redhat.com/errata/RHSA-2026:2456
RHSA-2026:2500 https://access.redhat.com/errata/RHSA-2026:2500
RHSA-2026:2563 https://access.redhat.com/errata/RHSA-2026:2563
RHSA-2026:2681 https://access.redhat.com/errata/RHSA-2026:2681
RHSA-2026:2695 https://access.redhat.com/errata/RHSA-2026:2695
RHSA-2026:2717 https://access.redhat.com/errata/RHSA-2026:2717
RHSA-2026:2718 https://access.redhat.com/errata/RHSA-2026:2718
RHSA-2026:2723 https://access.redhat.com/errata/RHSA-2026:2723
RHSA-2026:2728 https://access.redhat.com/errata/RHSA-2026:2728
RHSA-2026:2737 https://access.redhat.com/errata/RHSA-2026:2737
RHSA-2026:2754 https://access.redhat.com/errata/RHSA-2026:2754
RHSA-2026:2762 https://access.redhat.com/errata/RHSA-2026:2762
RHSA-2026:2764 https://access.redhat.com/errata/RHSA-2026:2764
RHSA-2026:2765 https://access.redhat.com/errata/RHSA-2026:2765
RHSA-2026:2800 https://access.redhat.com/errata/RHSA-2026:2800
RHSA-2026:2900 https://access.redhat.com/errata/RHSA-2026:2900
RHSA-2026:2919 https://access.redhat.com/errata/RHSA-2026:2919
RHSA-2026:2924 https://access.redhat.com/errata/RHSA-2026:2924
RHSA-2026:2925 https://access.redhat.com/errata/RHSA-2026:2925
RHSA-2026:2926 https://access.redhat.com/errata/RHSA-2026:2926
RHSA-2026:3296 https://access.redhat.com/errata/RHSA-2026:3296
RHSA-2026:3406 https://access.redhat.com/errata/RHSA-2026:3406
RHSA-2026:3444 https://access.redhat.com/errata/RHSA-2026:3444
RHSA-2026:3461 https://access.redhat.com/errata/RHSA-2026:3461
RHSA-2026:3462 https://access.redhat.com/errata/RHSA-2026:3462
RHSA-2026:3713 https://access.redhat.com/errata/RHSA-2026:3713
RHSA-2026:3782 https://access.redhat.com/errata/RHSA-2026:3782
RHSA-2026:3869 https://access.redhat.com/errata/RHSA-2026:3869
RHSA-2026:3874 https://access.redhat.com/errata/RHSA-2026:3874
RHSA-2026:4185 https://access.redhat.com/errata/RHSA-2026:4185
RHSA-2026:4215 https://access.redhat.com/errata/RHSA-2026:4215
RHSA-2026:4271 https://access.redhat.com/errata/RHSA-2026:4271
RHSA-2026:4466 https://access.redhat.com/errata/RHSA-2026:4466
RHSA-2026:4467 https://access.redhat.com/errata/RHSA-2026:4467
RHSA-2026:5807 https://access.redhat.com/errata/RHSA-2026:5807
RHSA-2026:6292 https://access.redhat.com/errata/RHSA-2026:6292
USN-7927-1 https://usn.ubuntu.com/7927-1/
USN-8010-1 https://usn.ubuntu.com/8010-1/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2025-66418.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H Found at https://github.com/urllib3/urllib3
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H Found at https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none


Vector: SSVCv2/E:N/A:Y/T:P/P:M/B:A/M:M/D:T/2025-12-05T16:15:39Z/ Found at https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H Found at https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none


Vector: SSVCv2/E:N/A:Y/T:P/P:M/B:A/M:M/D:T/2025-12-05T16:15:39Z/ Found at https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H Found at https://nvd.nist.gov/vuln/detail/CVE-2025-66418
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

Exploit Prediction Scoring System (EPSS)
Percentile 0.08088
EPSS Score 0.00029
Published At April 2, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T12:53:28.805796+00:00 GitLab Importer Import https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/urllib3/CVE-2025-66418.yml 38.0.0