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NVD / CVE Program· CNA mitre

CVE-2023-39975: kdc/do_tgs_req.c in MIT Kerberos 5 (aka krb5) 1.21 before 1.21.2 has a double free that is reachable if an authenticated user can trigger an…

HighCVSS 8.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 35/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.4% (FIRST EPSS); higher than 74% of all records.
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: krb5-devel (AlmaLinux:9) 1.21.1-1.el9; krb5-libs (AlmaLinux:9) 1.21.1-1.el9; krb5-pkinit (AlmaLinux:9) 1.21.1-1.el9.

Low priority for now. Upgrade to krb5-devel (AlmaLinux:9) 1.21.1-1.el9; krb5-libs (AlmaLinux:9) 1.21.1-1.el9; krb5-pkinit (AlmaLinux:9) 1.21.1-1.el9 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

kdc/do_tgs_req.c in MIT Kerberos 5 (aka krb5) 1.21 before 1.21.2 has a double free that is reachable if an authenticated user can trigger an authorization-data handling failure. Incorrect data is copied from one ticket to another.

Published
Aug 16, 2023
Updated
Jun 17, 2026
EPSS
1.4% · 74th percentile

Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2023-39975

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
mitkerberos 5

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • mit kerberos 51.21 and later · before 1.21.2

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:9krb5-develbefore 1.21.1-1.el91.21.1-1.el9
AlmaLinux:9krb5-libsbefore 1.21.1-1.el91.21.1-1.el9
AlmaLinux:9krb5-pkinitbefore 1.21.1-1.el91.21.1-1.el9
AlmaLinux:9krb5-serverbefore 1.21.1-1.el91.21.1-1.el9
AlmaLinux:9krb5-server-ldapbefore 1.21.1-1.el91.21.1-1.el9
AlmaLinux:9krb5-workstationbefore 1.21.1-1.el91.21.1-1.el9
AlmaLinux:9libkadm5before 1.21.1-1.el91.21.1-1.el9
openSUSE:Tumbleweedkrb5before 1.21.2-1.11.21.2-1.1
Red Hat:enterprise_linux:9::appstreamkrb5-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-debugsourcebefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-develbefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-libs-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-pkinit-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-server-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-server-ldap-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamkrb5-workstation-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::appstreamlibkadm5-debuginfobefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoskrb5before 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoskrb5-libsbefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoskrb5-pkinitbefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoskrb5-serverbefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoskrb5-server-ldapbefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoskrb5-workstationbefore 0:1.21.1-1.el90:1.21.1-1.el9
Red Hat:enterprise_linux:9::baseoslibkadm5before 0:1.21.1-1.el90:1.21.1-1.el9

+1

Same product

mit: all records

Other highest-scoring records for the same primary product.

  • CVE-2007-0956The telnet daemon (telnetd) in MIT krb5 before 1.6.1 allows remote attackers to bypass authentication and gain system access via a username…
    49Plan
  • CVE-2011-0285The process_chpw_request function in schpw.c in the password-changing functionality in kadmind in MIT Kerberos 5 (aka krb5) 1.7 through 1.9…
    46Plan
  • CVE-2001-0247Buffer overflows in BSD-based FTP servers allows remote attackers to execute arbitrary commands via a long pattern string containing a {}…
    46Plan

Published before and after this one in the same product

  • ← EarlierCVE-2022-42898Dec 25, 2022 · PAC parsing in MIT Kerberos 5 (aka krb5) before 1.19.4 and 1.20.x before 1.20.1 has integer overflows that may lead to remote code…
    37Monitor
  • ← EarlierCVE-2023-36054Aug 7, 2023 · lib/kadm5/kadm_rpc_xdr.c in MIT Kerberos 5 (aka krb5) before 1.20.2 and 1.21.x before 1.21.1 frees an uninitialized pointer.
    27Monitor
  • Later →CVE-2024-26458Feb 28, 2024 · Kerberos 5 (aka krb5) 1.21.2 contains a memory leak in /krb5/src/lib/rpc/pmap_rmt.c.
    21Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:krb5-devel1.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
almalinux:krb5-libs1.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
almalinux:krb5-pkinit1.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
almalinux:krb5-server1.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
almalinux:krb5-server-ldap1.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
almalinux:krb5-workstation1.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
almalinux:libkadm51.21.1-1.el9 · AlmaLinux:9Package registry (OSV)
opensuse:krb51.21.2-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:krb50:1.21.1-1.el9 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:krb5-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-debugsource0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-devel0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-libs0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:krb5-libs-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-pkinit0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::baseosPackage registry (OSV)
red hat:krb5-pkinit-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-server-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-server-ldap-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:krb5-workstation-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:libkadm5-debuginfo0:1.21.1-1.el9 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
rocky linux:krb50:1.21.1-10.el9_8 · Rocky Linux:9Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-415 · Double Free

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records