CVE-2021-37750

The Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.18.5 and 1.19.x before 1.19.3 has a NULL pointer dereference in kdc/do_tgs_req.c via a FAST inner body that lacks a server field.

Published: 2021-08-23 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-37750 is rated Moderate Risk (54.3/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.23%). Review affected assets and schedule remediation.

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

Exploit prediction scoring system (EPSS) score for CVE-2021-37750

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 2026-06-16 2.07% 2.23% +0.16%
2 2026-06-15 0.72% 2.07% +1.35%
3 2025-12-28 — 0.72% —

Full EPSS history (26 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-37750

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:L)
A normal user session is enough; they don’t have to be admin.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/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:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-37750

OS Trackers for CVE-2021-37750

vendor priority summary link
alpine medium CVE-2021-37750: 1 source package rows (krb5); 8 state rows across 8 repos (3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 0. https://security.alpinelinux.org/vuln/CVE-2021-37750
debian not yet assigned CVE-2021-37750 not yet assigned priority: Debian including 1 source packages (krb5), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-37750
gentoo normal CVE-2021-37750: 1 GLSA(s) (202405-11), 1 atom(s) (app-crypt/mit-krb5); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-37750
redhat medium — https://access.redhat.com/security/cve/CVE-2021-37750
suse medium CVE-2021-37750 severity moderate: SUSE including 396 source package names (0.1.0:krb5-1.16.3-3.24.1, 0.1.75:krb5-1.16.3-3.24.1, …), 711 product×package rows across 138 product lines (Container caasp/v4/389-ds, Container caasp/v4/busybox, … (138 product lines)): Fixed 326, Known Not Affected 231, Known Affected 154. https://www.suse.com/security/cve/CVE-2021-37750/
ubuntu medium CVE-2021-37750 medium priority: Ubuntu including 1 source packages (krb5), 13 status rows across 13 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, trusty, upstream, xenial): not-affected 8, released 3, ignored 2. https://ubuntu.com/security/CVE-2021-37750

Affected software / configurations for CVE-2021-37750

Vendor Product Version Raw CPE
mit kerberos_5 < 1.18.5 cpe:2.3:a:mit:kerberos_5:*:*:*:*:*:*:*:*
mit kerberos_5 >= 1.19.0, < 1.19.3 cpe:2.3:a:mit:kerberos_5:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
starwindsoftware starwind_virtual_san v8r13 cpe:2.3:a:starwindsoftware:starwind_virtual_san:v8r13:14338:*:*:*:*:*:*
oracle communications_cloud_native_core_network_slice_selection_function 22.1.0 cpe:2.3:a:oracle:communications_cloud_native_core_network_slice_selection_function:22.1.0:*:*:*:*:*:*:*

References for CVE-2021-37750

cvelogic Threat Intelligence