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Not in CISA KEV
HIGH severity

CVE-2020-1967 — openssl-src

HIGH

CVE-2020-1967 is a high-severity (CVSS 7.5) NULL Pointer Dereference vulnerability in openssl-src. 3 public exploit references exist, so weaponization risk is real. A fix is available for openssl-src — see the affected versions and patch details below.

Null pointer deference in openssl-src

Also known asGHSA-jq65-29v4-4x35RUSTSEC-2020-0015
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
3 known
Exploitation data as of Oct 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2020-1967.

EPSS Exploitation Probability

via FIRST.org ↗
53.3%probability of exploitation in next 30 days
High Risk0.00%
Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk
49.1%56.6%64.0%71.5%67.3%53.3%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-1967 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🦀openssl-src

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

Description

Server or client applications that call the SSL_check_chain() function during or after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a result of incorrect handling of the "signature_algorithms_cert" TLS extension. The crash occurs if an invalid or unrecognised signature algorithm is received from the peer. This could be exploited by a malicious peer in a Denial of Service attack. OpenSSL version 1.1.1d, 1.1.1e, and 1.1.1f are affected by this issue. This issue did not affect OpenSSL versions prior to 1.1.1d. Fixed in OpenSSL 1.1.1g (Affected 1.1.1d-1.1.1f).

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.ioopenssl-src≥ 111.6.0&&< 111.9.0111.9.0cargo update -p openssl-src --precise 111.9.0

Affected Products

26 products · 38 configurations
OS
fabric operating systembroadcom
all
OS
debian linuxdebian
2 versions
9.010.0
OS
fedorafedoraproject
3 versions
303132
OS
freebsdfreebsd
1 version
12.1
Application
enterpriseonejdedwards
< 9.2.5.0
range
Application
active iq unified managernetapp
≥ 9.5
range
Exploits & PoCs
3

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Server or client applications that call the SSL_check_chain() function d…

github.comNVDJul 2021

Server or client applications that call the SSL_check_chain() function d…

github.comGithubApr 2020

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openssl-src, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update openssl-src to 111.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-1967 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This flaw was introduced by the following OpenSSL commit: https://github.com/openssl/openssl/commit/5235ef44b93306a14d0b6c695b13c64b16e1fdec which was shipped as a part of OpenSSL-1.1.1d, therefore older versions are not affected by this flaw. OpenSSL packages shipped with Red Hat Products are NOT affected by this…

Workaround published by Red Hat
Applications compiled with OpenSSL >= 1.1.1d that either use openssl without invoking the `SSL_check_chain()` function or do not use TLS 1.3 are not vulnerable to this flaw.
Source: Red Hat security advisory for CVE-2020-1967 (CC BY 4.0)

Frequently Asked Questions

Server or client applications that call the SSL_check_chain() function during or after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a result of incorrect handling of the "signature_algorithms_cert" TLS extension. The crash occurs if an invalid or unrecognised signature algorithm is received from the peer. This could be exploited by a malicious peer in a Denial of Service attack. OpenSSL version 1.1.1d, 1.1.1e, and 1.1.1f are affected by this issue. This issue did not affect OpenSSL versions prior to 1.1.1d. Fixed in OpenSSL 1.1.1g (Affected 1.1.1d-1.1.1f).
O3 Security · Impact-Aware SCA

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CVE-2020-1967: openssl-src DoS — Fixed in 111.9.0