What is the CVSS score of CVE-2021-31826?

CVE-2021-31826 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 2.0%.

Is there a public PoC exploit available for CVE-2021-31826?

Yes, a public proof-of-concept exploit is available for CVE-2021-31826. Prioritise patching immediately. EPSS: 2.0%.

Shibboleth CVE-2021-31826

HIGH

NULL Pointer Dereference (CWE-476)

2021-04-27 cve@mitre.org

Denial Of Service Null Pointer Dereference Service Provider Shibboleth

7.5

CVSS 3.1 · NVD

View

Vulnerability Assessment

Weakness	CWE CWE-476 OWASP Top 10:2025 A10:2025 - Mishandling of Exceptional Conditions ASVS 5.0 V16 - Security Logging and Error Handling Null pointer safety, defensive checks MITRE ATT&CK 1 technique across 1 tactic: Impact The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	A remote attacker could crash the application by dereferencing a null pointer by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

No patch listed yet 2.0% exploitation probability (EPSS)

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AnalysisAI

Shibboleth Service Provider 3.x before 3.2.2 is prone to a NULL pointer dereference flaw involving the session recovery feature. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Check pointers before dereferencing. Use static analysis tools to detect null pointer paths.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as NULL Pointer Dereference (CWE-476), which allows attackers to crash the application by dereferencing a null pointer. Shibboleth Service Provider 3.x before 3.2.2 is prone to a NULL pointer dereference flaw involving the session recovery feature. The flaw is exploitable (for a daemon crash) on systems not using this feature if a crafted cookie is supplied. Affected products include: Shibboleth Service Provider. Version information: before 3.2.2.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.5 HIGH

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

DescriptionNVD

Shibboleth Service Provider 3.x before 3.2.2 is prone to a NULL pointer dereference flaw involving the session recovery feature. The flaw is exploitable (for a daemon crash) on systems not using this feature if a crafted cookie is supplied.

Threat Intelligence Overview

EPSS Score

2.0%

Top 22% exploitable

Exploit

POC

Public exploit code exists

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 2.0%

Patch available No

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +2

CVSS: +38

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Null Pointer Dereference MEDIUM

A null pointer dereference occurs when a program attempts to access memory through a pointer that has been set to NULL (address 0x0).

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)NVD

cpe:2.3:a:shibboleth:service_provider:*:*:*:*:*:*:*:*

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Same weakness CWE-476 – NULL Pointer Dereference

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References

Advisories & patches

ADVISORY https://shibboleth.net/community/advisories/secadv_20210426.txt REF https://bugs.debian.org/987608 REF https://git.shibboleth.net/view/?p=cpp-sp.git%3Ba=commit%3Bh=5a47c3b9378f4c49392dd4d15189b70956f9f2ec REF https://www.debian.org/security/2021/dsa-4905

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