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CVE-2020-1967

51
FAUCET Score

CVE-2020-1967 is a high-severity Denial of Service (DoS) vulnerability affecting OpenSSL versions 1.1.1d through 1.1.1f, specifically impacting server or client applications that call SSL_check_chain() during or after a TLS 1.3 handshake. This flaw, a NULL pointer dereference (CWE-476), occurs when an invalid or unrecognized signature algorithm is received from a peer, leading to application crashes. With a CVSS score of 7.5 (HIGH), the vulnerability is easily exploitable over the network with low attack complexity and no user interaction required, resulting in a complete loss of availability. Although no active exploitation has been confirmed and public exploit code (Metasploit, Nuclei, ExploitDB) is unavailable, the vulnerability has garnered significant community discussion and media coverage, including reports of a Proof-of-Concept (PoC) exploit.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.1.1d, <= 1.1.1fCPE matchmatch criteria
cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
12.1CPE matchmatch criteria
cpe:2.3:o:freebsd:freebsd:12.1:-:*:*:*:*:*:*
30CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*

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
53.34%
Probability of exploitation in next 30 days
EPSS Percentile
98.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.5334 is in the 98th percentile among its peer group of 51,485 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

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

Remediation

Patch Available

Vendor Patches (2)

oraclepatch availablevia nvd_reference
View patch
rustpatch availablevia ghsa
Product: openssl-srcFixed in: 111.9.0

Vendor Advisories (2)

rustGHSA-jq65-29v4-4x35high

Null pointer deference in openssl-src

Aug 25, 2021
redhatCVE-2020-1967Important

openssl: Segmentation fault in SSL_check_chain causes denial of service

Apr 21, 2020

References

lists.opensuse.org / opensuse-security-announce/2020-07/msg00004.html
Mailing ListThird Party Advisory
lists.opensuse.org / opensuse-security-announce/2020-07/msg00011.html
Mailing ListThird Party Advisory
packetstormsecurity.com / files/157527/OpenSSL-signature_algorithms_cert-Denial-Of-Service.html
Third Party AdvisoryVDB Entry
seclists.org / fulldisclosure/2020/May/5
Mailing ListThird Party Advisory
github.com / irsl/CVE-2020-1967
ExploitThird Party Advisory
git.openssl.org / gitweb
kb.pulsesecure.net / articles/Pulse_Security_Advisories/SA44440
Third Party Advisory
lists.apache.org / thread.html/r66ea9c436da150683432db5fbc8beb8ae01886c6459ac30c2cea7345%40%3Cdev.tomcat.apache.org%3E
lists.apache.org / thread.html/r94d6ac3f010a38fccf4f432b12180a13fa1cf303559bd805648c9064%40%3Cdev.tomcat.apache.org%3E
lists.apache.org / thread.html/r9a41e304992ce6aec6585a87842b4f2e692604f5c892c37e3b0587ee%40%3Cdev.tomcat.apache.org%3E
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/DDHOAATPWJCXRNFMJ2SASDBBNU5RJONY
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/EXDDAOWSAIEFQNBHWYE6PPYFV4QXGMCD
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/XVEP3LAK4JSPRXFO4QF4GG2IVXADV3SO
security.freebsd.org / advisories/FreeBSD-SA-20:11.openssl.asc
PatchThird Party Advisory
security.gentoo.org / glsa/202004-10
Third Party Advisory
security.netapp.com / advisory/ntap-20200424-0003
Third Party Advisory
security.netapp.com / advisory/ntap-20200717-0004
Third Party Advisory
debian.org / security/2020/dsa-4661
Third Party Advisory
openssl.org / news/secadv/20200421.txt
Vendor Advisory
oracle.com / security-alerts/cpuApr2021.html
PatchThird Party Advisory
oracle.com / security-alerts/cpujan2021.html
PatchThird Party Advisory
oracle.com / security-alerts/cpujul2020.html
Third Party Advisory
oracle.com / /security-alerts/cpujul2021.html
PatchThird Party Advisory
oracle.com / security-alerts/cpuoct2020.html
PatchThird Party Advisory
oracle.com / security-alerts/cpuoct2021.html
PatchThird Party Advisory
synology.com / security/advisory/Synology_SA_20_05
Third Party Advisory
synology.com / security/advisory/Synology_SA_20_05_OpenSSL
Third Party Advisory
tenable.com / security/tns-2020-03
Third Party Advisory
tenable.com / security/tns-2020-04
Third Party Advisory
tenable.com / security/tns-2020-11
Third Party Advisory
tenable.com / security/tns-2021-10
Third Party Advisory
openwall.com / lists/oss-security/2020/04/22/2
Mailing ListThird Party Advisory