CVE Intelligence
Medium Injection exploit reference

CVE-2021-23336 — Web Cache Poisoning

The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable to Web Cache Poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by using a vector called parameter cloaking. When the attacker can separate query parameters using a semicolon (;), they can cause a difference in the interpretation of the request between the proxy (running with default configuration) and the server. This can result in malicious requests being cached as completely safe ones, as the proxy would usually not see the semicolon as a separator, and therefore would not include it in a cache key of an unkeyed parameter.

Published Feb 15, 2021 · Updated Oct 14, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: snyk

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 40.7% (30-day exploitation probability)+15
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
40.74%
ahead of 99% of scored CVEs · Oct 14, 2026
Affects
Debian
Debian Linux and 11 more
CVSS base
5.9
Medium · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — www.openwall.com (NIST National Vulnerability Database)
  • Documented patch — github.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Debian Debian Linux, Djangoproject Django, Fedoraproject Fedora…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  5. EPSS ahead of 99% of scored CVEs: prioritize it in the patch queue.
  6. Search available logs for exploit probes matching the vulnerability class (injection), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Debian Debian Linux version 9.0 Vulnerable NIST National Vulnerability Database
Djangoproject Django ≥ 2.2 and < 2.2.19≥ 3.0 and < 3.0.13≥ 3.1 and < 3.1.7 Vulnerable NIST National Vulnerability Database
Fedoraproject Fedora version 33version 34version 32 Vulnerable NIST National Vulnerability Database
Netapp Cloud Backup versions not specified by the source Vulnerable NIST National Vulnerability Database
Netapp Inventory Collect Tool versions not specified by the source Vulnerable NIST National Vulnerability Database
Netapp Ontap Select Deploy Administration Utility versions not specified by the source Vulnerable NIST National Vulnerability Database
Netapp Snapcenter versions not specified by the source Vulnerable NIST National Vulnerability Database
Oracle Communications Offline Mediation Controller version 12.0.0.3.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Pricing Design Center version 12.0.0.3.0 Vulnerable NIST National Vulnerability Database
Oracle Enterprise Manager Ops Center version 12.4.0.0 Vulnerable NIST National Vulnerability Database
Oracle Zfs Storage Appliance version 8.8 Vulnerable NIST National Vulnerability Database
Python Python < 3.6.13≥ 3.7.0 and < 3.7.10≥ 3.8.0 and < 3.8.8≥ 3.9.0 and < 3.9.2 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.9 CVSS 3.1 Medium 1.6 4.2 report@snyk.io via NIST National Vulnerability Database
5.9 CVSS 3.1 Medium 1.6 4.2 nvd@nist.gov via NIST National Vulnerability Database
5.9 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
5.9 CVSS 3.1 Medium — — snyk via CVE Program (cve.org) e CISA ADP
4.0 CVSS 2.0 Medium 4.9 4.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-444 · HTTP Request Smuggling

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 40.74%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Look for parameters with command/query metacharacters and unexpected child processes of the service.
web/proxy/WAF logsnetwork IDS/IPSapplication logsendpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 14, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 14, 2026
  • Fix documented
    Oct 14, 2026 · NIST National Vulnerability Database
  • Affected products added · python/python, fedoraproject/fedora, debian/debian linux, netapp/cloud backup, netapp/inventory collect tool, netapp/ont
    Oct 14, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.9
    Oct 14, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 14, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 14, 2026 · Alertas do Telegram
  • 2021
  • CVE published
    Feb 15, 2021 · snyk

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 14, 2026 – Oct 14, 2026
  • 1× Official description updated · Oct 14, 2026 – Oct 14, 2026

References

62 on the record

Elsewhere on this site

Debian
every CVE for this vendor
Injection
same class
CWE-444
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-87890 Potential request forgery via spatial lookup byte values 9d
  • CVE-2026-87975 Privilege abuse in model formsets with editable primary keys 9d
  • CVE-2026-77050 Potential denial-of-service vulnerability in get_supported_language_variant() 9d
  • CVE-2026-84429 Potential denial-of-service vulnerability in HTTP header parsing 9d
  • CVE-2026-15920 Potential cross-site scripting via URLField values in the admin Aug 4, 2026
  • CVE-2026-15307 Server-side file-write and request forgery via spatial lookups Aug 4, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-23336 is "Web Cache Poisoning", rated Medium. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.9 describes technical severity. EPSS 40.74% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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