CVE-2021-20231

Exp

A flaw was found in gnutls. A use after free issue in client sending key_share extension may lead to memory corruption and other consequences.

Published: 2021-03-12 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20231 is rated High Exploit Risk (87.7/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 3.75%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +2.56% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-20231

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-20231

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 1.20% 3.75% +2.56%
2 2026-04-12 0.94% 1.20% +0.25%
3 2025-11-22 — 0.94% —

Full EPSS history (24 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20231

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2021-20231

OS Trackers for CVE-2021-20231

vendor priority summary link
alpine critical CVE-2021-20231: 1 source package rows (gnutls); 35 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 10, open 25. https://security.alpinelinux.org/vuln/CVE-2021-20231
debian not yet assigned CVE-2021-20231 not yet assigned priority: Debian including 1 source packages (gnutls28), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-20231
redhat medium — https://access.redhat.com/security/cve/CVE-2021-20231
suse high CVE-2021-20231 severity important: SUSE including 396 source package names (0.1.0:libgnutls30-3.6.7-6.40.2, 0.1.75:libgnutls30-3.6.7-6.40.2, …), 656 product×package rows across 160 product lines (Container caasp/v4/389-ds, Container caasp/v4/busybox, … (160 product lines)): Fixed 436, Known Affected 135, Known Not Affected 85. https://www.suse.com/security/cve/CVE-2021-20231/
ubuntu low CVE-2021-20231 low priority: Ubuntu including 1 source packages (gnutls28), 9 status rows across 9 suites (bionic, focal, groovy, hirsute, impish, jammy, trusty, upstream, xenial): not-affected 5, released 2, DNE 1, ignored 1. https://ubuntu.com/security/CVE-2021-20231

Affected software / configurations for CVE-2021-20231

Vendor Product Version Raw CPE
gnu gnutls >= 3.6.3, < 3.7.1 cpe:2.3:a:gnu:gnutls:*:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
netapp active_iq_unified_manager — cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*
netapp e-series_performance_analyzer — cpe:2.3:a:netapp:e-series_performance_analyzer:-:*:*:*:*:*:*:*

References for CVE-2021-20231

URL Tags
https://bugzilla.redhat.com/show_bug.cgi?id=1922276 Issue Tracking Patch Third Party Advisory
https://lists.apache.org/thread.html/r50661d6f0082709aad9a584431b59ec364f9974b63b07e0800230168%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/r5d4001031e7790d8c6396c499522b4ed2aab782da87b1a14184793bb%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/r5f88bed447742fcc5c47bf1c7be965ef450131914a6e1f85feba2779%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/r6ac143ba6dd98bd4bf6bf010d46e56e254056459721ba18822d611f7%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/r9cbc69e57276413788e90a6ee16c7c034ea4258d31935b70db2bd158%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/rcd70a4c88a47a75fd2d5f3ffb7cee8c2a18c713320bd90fdcb57495f%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/rf5e1256d870193def4a82ad89ab95e63943a313b5ff0d81aa87e4532%40%3Cissues.spark.apache.org%3E
https://lists.apache.org/thread.html/rfd5273d72d244178441e6904a2f2b41a3268f569e8092ea0b3b2bb20%40%3Cissues.spark.apache.org%3E
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OSLAE6PP33A7VYRYMYMUVB3U6B26GZER/
https://security.netapp.com/advisory/ntap-20210416-0005/ Third Party Advisory
https://www.gnutls.org/security-new.html#GNUTLS-SA-2021-03-10 Exploit Vendor Advisory
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