An issue was discovered in urllib3 before 1.26.5.
An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.
- BDU:2022-00586
- GHSA-q2q7-5pp4-w6pg
- ALSA-2021:4160
- ALSA-2021:4162
- openSUSE-SU-2021:2012-1
- openSUSE-SU-2024:11277-1
- openSUSE-SU-2024:14055-1
- PYSEC-2021-108
- RHSA-2021:3254
- RHSA-2021:3473
- RHSA-2021:4160
- RHSA-2021:4162
- RHSA-2021:4702
- RLSA-2021:4160
- RLSA-2021:4162
- SUSE-RU-2021:2194-1
- SUSE-SU-2021:2012-1
- SUSE-SU-2021:2195-1
- Published
- Jun 29, 2021
- Updated
- Jun 16, 2026
- EPSS
- 3.3% · 88th percentile
- CWE
- CWE-400
Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 3.3%
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| python | urllib3 | cpe:2.3:a:python:urllib3 |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| oracle | enterprise manager ops center | cpe:2.3:a:oracle:enterprise_manager_ops_center |
| oracle | instantis enterprisetrack | cpe:2.3:a:oracle:instantis_enterprisetrack |
| oracle | zfs storage appliance kit | cpe:2.3:a:oracle:zfs_storage_appliance_kit |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- fedoraproject fedora33
- fedoraproject fedora34
- oracle enterprise manager ops center12.4.0.0
- oracle instantis enterprisetrack17.1
- oracle instantis enterprisetrack17.2
- oracle instantis enterprisetrack17.3
- oracle zfs storage appliance kit8.8
- python urllib31.25.4 and later · before 1.26.5
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | python38-asn1crypto | before 1.2.0-3.module_el8.6.0+2778+cd494b30 | 1.2.0-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-atomicwrites | before 1.3.0-8.module_el8.6.0+2778+cd494b30 | 1.3.0-8.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-attrs | before 19.3.0-3.module_el8.6.0+2778+cd494b30 | 19.3.0-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-babel | before 2.7.0-11.module_el8.6.0+2778+cd494b30 | 2.7.0-11.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-cffi | before 1.13.2-3.module_el8.6.0+2778+cd494b30 | 1.13.2-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-chardet | before 3.0.4-19.module_el8.6.0+2778+cd494b30 | 3.0.4-19.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-cryptography | before 2.8-3.module_el8.6.0+2778+cd494b30 | 2.8-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-Cython | before 0.29.14-4.module_el8.6.0+2778+cd494b30 | 0.29.14-4.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-idna | before 2.8-6.module_el8.6.0+2778+cd494b30 | 2.8-6.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-jinja2 | before 2.10.3-5.module_el8.6.0+2778+cd494b30 | 2.10.3-5.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-markupsafe | before 1.1.1-6.module_el8.6.0+2778+cd494b30 | 1.1.1-6.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-mod_wsgi | before 4.6.8-3.module_el8.6.0+2778+cd494b30 | 4.6.8-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-more-itertools | before 7.2.0-5.module_el8.6.0+2778+cd494b30 | 7.2.0-5.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-numpy | before 1.17.3-6.module_el8.6.0+2778+cd494b30 | 1.17.3-6.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-numpy-doc | before 1.17.3-6.module_el8.6.0+2778+cd494b30 | 1.17.3-6.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-numpy-f2py | before 1.17.3-6.module_el8.6.0+2778+cd494b30 | 1.17.3-6.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-packaging | before 19.2-3.module_el8.6.0+2778+cd494b30 | 19.2-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-pluggy | before 0.13.0-3.module_el8.6.0+2778+cd494b30 | 0.13.0-3.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-ply | before 3.11-10.module_el8.6.0+2778+cd494b30 | 3.11-10.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-psutil | before 5.6.4-4.module_el8.6.0+2778+cd494b30 | 5.6.4-4.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-psycopg2 | before 2.8.4-4.module_el8.6.0+2778+cd494b30 | 2.8.4-4.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-psycopg2-doc | before 2.8.4-4.module_el8.6.0+2778+cd494b30 | 2.8.4-4.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-psycopg2-tests | before 2.8.4-4.module_el8.6.0+2778+cd494b30 | 2.8.4-4.module_el8.6.0+2778+cd494b30 |
| AlmaLinux:8 | python38-py | before 1.8.0-8.module_el8.6.0+2778+cd494b30 | 1.8.0-8.module_el8.6.0+2778+cd494b30 |
+96
Same product
python: all recordsOther highest-scoring records for the same primary product.
- CVE-2018-20060urllib3 before version 1.23 does not remove the Authorization HTTP header when following a cross-origin redirect (i.e., a redirect that diff40Plan
- CVE-2026-21441urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)36Monitor
- CVE-2026-44432urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API35Monitor
- CVE-2025-66471urllib3 Streaming API improperly handles highly compressed data35Monitor
- CVE-2025-66418urllib3 allows an unbounded number of links in the decompression chain35Monitor
- CVE-2026-44431urllib3: Sensitive headers forwarded across origins in proxied low-level redirects32Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:python39-attrs | 20.3.0-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-cffi | 1.14.3-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-chardet | 3.0.4-19.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-cryptography | 3.3.1-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-Cython | 0.29.21-5.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-idna | 2.10-3.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-iniconfig | 1.1.1-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-mod_wsgi | 4.7.1-4.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-more-itertools | 8.5.0-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-numpy | 1.19.4-3.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-numpy-doc | 1.19.4-3.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-PyMySQL | 0.10.1-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| debian:python-urllib3 | 1.26.5-1~exp1 · Debian:12 | Package registry (OSV) |
| opensuse:python-urllib3 | 1.25.10-4.3.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| PyPI:urllib3 | 1.26.5 | Package registry (OSV) |
| red hat:rh-python38-babel | 0:2.7.0-12.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python | 0:3.8.11-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-babel | 0:2.7.0-12.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-cryptography | 0:2.8-5.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-cryptography-debuginfo | 0:2.8-5.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-debug | 0:3.8.11-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-debuginfo | 0:3.8.11-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-devel | 0:3.8.11-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-idle | 0:3.8.11-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-jinja2 | 0:2.10.3-6.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-libs | 0:3.8.11-2.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| red hat:rh-python38-python-lxml | 0:4.4.1-7.el7 · Red Hat:rhel_software_collections:3::el7 | Package registry (OSV) |
| rocky linux:Cython | 0:0.29.21-5.module+el8.4.0+574+843c4898 · Rocky Linux:8 | Package registry (OSV) |
| rocky linux:mod_wsgi | 0:4.7.1-4.module+el8.4.0+574+843c4898 · Rocky Linux:8 | Package registry (OSV) |
| rocky linux:numpy | 0:1.19.4-3.module+el8.5.0+673+10283621 · Rocky Linux:8 | Package registry (OSV) |
+21
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-21-0701 · Sep 3, 2021(IBM Güvenlik Bülteni Yayınladı)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-400 · Uncontrolled Resource ConsumptionCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvd-primary
Root cause
Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.
The bug in code
The whole CWE-400 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
function expand(node) { return node.children.map(expand);}Fixed
const MAX_DEPTH = 32;function expand(node, depth = 0) { if (depth > MAX_DEPTH) throw new Error("too deep"); return node.children.map((c) => expand(c, depth + 1));}Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/advisories/GHSA-q2q7-5pp4-w6pg
- github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6SCV7ZNAHS3E6PBFLJGENCDRDRWRZZ6W/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FMUGWEAUYGGHTPPXT6YBD53WYXQGVV73/
- security.gentoo.org/glsa/202107-36
- www.oracle.com/security-alerts/cpuoct2021.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.