Home/CVE/HTTP header injection vulnerability in Everything version 1.0, 1.1, and 1.2 except the Lite version may allow a remote a
CVE
CVE-2021-20784
HTTP header injection vulnerability in Everything version 1.0, 1.1, and 1.2 except the Lite version may allow a remote a
HTTP header injection vulnerability in Everything version 1.0, 1.1, and 1.2 except the Lite version may allow a remote attacker to inject an arbitrary script or alter the website that uses the product.
MEDIUM · CVSS 6.1
EPSS 0.01118
EPSS exploitation odds1.12% · top 38%
Monitor
- No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
No Sigma yet — build one →
YARA rules0
Look this up elsewhere - one-click external pivots
▸
How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2021-20784, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked.
EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal.
CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score.
Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits.
PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
EPSS exploitation probability
1.12%
Top 38%odds of exploitation in the next 30 days
CVSS metric silhouette
shape grows toward worst-case
SSVC triage
No SSVC vulnrichment for this CVE. CISA's Vulnrichment program scores newer CVEs (~2024 onwards) plus selected older critical ones. Use the EPSS probability + KEV status to triage instead.
CVSS vector breakdown
Exploitability - how they get in
Attack Vector
Network
Adjacent
Local
Physical
Attack Complexity
Low
High
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Impact - what breaks
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
VECTOR
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NLifecycle
- 14 Jul 2021Published to NVD
- 17 Jun 2026Last modified
Every entry is a recorded date - NVD publish/modify, CISA KEV add, public exploit disclosure. No inferred events.
Attack path
Full kill chain
◆
ATT&CK techniques
2Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.
▤ Build a SIEM detection for these techniques⬡
Weakness Classification
▤
Affected Products & Versions
3▤
Related CVEs
6CVEs linked to this one by a shared weakness (CWE) or affected product - joins on data already in the engine, with the reason shown per row. Not a guess.
CVE-2017-6031
A Header Injection issue was discovered in Certec EDV GmbH atvise scada prior to...
same CWE-644
HIGH
CVE-2020-6982
In Honeywell WIN-PAK 4.7.2, Web and prior versions, the header injection vulnera...
same CWE-644
HIGH
CVE-2021-21265
October is a free, open-source, self-hosted CMS platform based on the Laravel PH...
same CWE-644
MEDIUM
CVE-2021-41114
TYPO3 is an open source PHP based web content management system released under t...
same CWE-644
MEDIUM
CVE-2020-24567
voidtools Everything before 1.4.1 Beta Nightly 2020-08-18 allows privilege escal...
same product
HIGH
CVE-2023-27704
Void Tools Everything lower than v1.4.1.1022 was discovered to contain a Regular...
same product
MEDIUM
🔗
References & Sources
4Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.