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CVE-2020-5591

25
FAUCET Score

CVE-2020-5591 is a denial-of-service vulnerability affecting XACK DNS versions 1.11.0 to 1.11.4, 1.10.0 to 1.10.8, 1.8.0 to 1.8.23, 1.7.0 to 1.7.18, and earlier versions. This flaw allows remote attackers to degrade recursive resolver performance or use the resolver in reflection attacks. Rated 7.5 HIGH on the CVSS scale, it is easily exploitable over the network with low attack complexity, leading to high availability impact. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.7.18CPE matchmatch criteria
cpe:2.3:a:xack:xack_dns:*:*:*:*:*:*:*:*
>= 1.8.0, <= 1.8.23CPE matchmatch criteria
cpe:2.3:a:xack:xack_dns:*:*:*:*:*:*:*:*
>= 1.10.0, <= 1.10.8CPE matchmatch criteria
cpe:2.3:a:xack:xack_dns:*:*:*:*:*:*:*:*
>= 1.11.0, <= 1.11.4CPE matchmatch criteria
cpe:2.3:a:xack:xack_dns:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.64%
Probability of exploitation in next 30 days
EPSS Percentile
73.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0164 is in the 56th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

jvn.jp / en/jp/JVN40208370/index.html
MitigationThird Party AdvisoryVDB Entry
xack.co.jp / info
Vendor Advisory