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CVE Record

CVE-2020-28196: MIT Kerberos 5 (aka krb5) before 1.17.2 and 1.18.x before 1.18.3 allows unbounded recursion via an ASN.1-en...

MIT Kerberos 5 (aka krb5) before 1.17.2 and 1.18.x before 1.18.3 allows unbounded recursion via an ASN.1-encoded Kerberos message because the lib/krb5/asn.1/asn1_encode.c support for BER indefinite lengths lacks a recursion limit.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This flaw can let an unauthenticated network sender crash or exhaust a vulnerable MIT Kerberos implementation by abusing how it handles specially encoded Kerberos messages. The business impact is availability: authentication-dependent services may be disrupted, but the supplied sources do not indicate data theft or integrity compromise.

Executive priority

Prioritize remediation where Kerberos supports critical login, domain, or service authentication paths. The issue is not described as data-compromising, but authentication outages can create broad business disruption if central infrastructure is affected.

Technical view

MIT krb5 before 1.17.2 and 1.18.x before 1.18.3 lacks a recursion limit when ASN.1 BER indefinite lengths are encoded. This maps to CWE-674 and can cause uncontrolled recursion from network-reachable Kerberos message parsing, with CVSS 3.1 score 7.5 for high availability impact.

Likely exposure

Exposure is most likely where MIT krb5 packages or embedded Kerberos components are present, including Linux distributions and vendor products that shipped affected krb5 versions. The bundle does not provide a complete affected-product matrix, so asset inventory and vendor advisories are necessary.

Exploitation context

The CVSS vector indicates remote, unauthenticated, low-complexity availability impact. The supplied bundle marks KEV as false and provides no cited evidence of active exploitation. Treat it as a denial-of-service risk rather than proven in-the-wild compromise.

Researcher notes

The core issue is uncontrolled recursion in ASN.1 BER indefinite-length handling in krb5 encoding support. The provided commit and distribution advisories support a patch-based remediation path. Public bundle evidence is strong for cause and version bounds, but incomplete for all downstream affected products.

Mitigation direction

  • Upgrade MIT krb5 to 1.17.2, 1.18.3, or vendor-fixed packages.
  • Apply Debian, Fedora, Gentoo, Oracle, or NetApp updates where applicable.
  • Check vendor advisories for embedded or appliance-specific remediation guidance.
  • Prioritize externally reachable Kerberos services and critical authentication infrastructure.
  • Monitor Kerberos service health and authentication failure spikes during remediation.

Validation and detection

  • Inventory installed krb5 package versions across servers, containers, and appliances.
  • Confirm versions are not before 1.17.2 or affected 1.18.x releases.
  • Review distribution security advisories for fixed package build numbers.
  • Check vendor advisories for products bundling MIT krb5.
  • Verify authentication services remain stable after patching.
Prepared
Confidence
high
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-674: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2020-28196 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
15Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2020-28196Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

CWE-674

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-674 · source CWE mapping

Uncontrolled Recursion

Uncontrolled Recursion represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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