Page generated: 09 Nov 2026, 10:49 UTC
CVE-2021-31207
Microsoft Exchange Server Security Feature Bypass Vulnerability
CVSS 6.6 (MEDIUM) KEV: KNOWN CATALOG
Attention and evidence
HYPE SCORE
0.0/10
REALITY · THREAT PRIORITY
8.5/10
General review priority; not probability
Evidence confidence: Exploitation recorded
Sources: 11 documents and public datasets.
Hype components
Headline sample (25%)
0/100
Press, 30 days (60%)
0/100
Grounded branding (15%)
0/100
HYPE TOTAL0/100
Sources and documents
Barracuda Blog
Press · 05 Dec 2025, 08:00 · Cybersecurity Threat Advisory: Global Microsoft Exchange attack - Barracuda Blog
SC Media
Press · 31 Jul 2024, 07:00 · UK electoral agency cyberattack prompted by security failings - SC Media
Qualys
Press · 06 May 2022, 07:00 · CISA Alert: Top 15 Routinely Exploited Vulnerabilities - Qualys
Google Cloud
Press · 17 Nov 2021, 08:00 · ProxyNoShell: A Change in Tactics Exploiting ProxyShell Vulnerabilities - Google Cloud
Google Cloud
Press · 02 Sep 2021, 07:00 · PST, Want a Shell? ProxyShell Exploiting Microsoft Exchange Servers - Google Cloud
Score evolution
● Hype ● Reality
Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.
First record: hype 0.0 · reality 8.5 (2026-11-02 15:12). The curve appears once the score changes.
Public exploit evidence
1
Public exploit entries / repo candidates
Evidence context and dated references
Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs.
Evidence in context
- Confidence in exploitation evidence
- Exploitation recorded
- Priority basis
- Recorded exploitation; CVSS 6.6; EPSS 99.8%
- Attention, last 30 days
- 0 distinct story titles; 0 press documents; 0 publisher domains.
- Technical potential
- network access, high privileges, no user interaction, additional attack conditions.
- Observed activity
- Exploitation recorded in CISA KEV.
- Known scale
- Not quantified.
- Evidence confidence basis
- Trusted exploitation confirmation
Score evaluated: 2026-11-05 13:58:26.907878+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z
Source event timeline
Published
11 May 2021, 19:11
First press mention
12 May 2021, 07:00
Added to the CISA KEV catalog
03 Nov 2021, 00:00
Latest press mention
05 Dec 2025, 08:00
Score calculated
05 Nov 2026, 13:58
PoCs on GitHub
1 repositories