BlackTreeCVE Intelligence
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Full vulnerability report · 2006
CVE-2006-5051High confidence

Affected product: Double Free

Unknown · Unknown

8.1HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Mitigation available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 22 Oct 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 44.96% for the current model date.

Compensating controls

  • Apply the linked authoritative mitigation while planning the permanent fix.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Unknown Unknown and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

4 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:4.6p1-1Debian Security Tracker ↗Source updated 22 Oct 2026
Debian bookwormbookworm · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:4.6p1-1Debian Security Tracker ↗Source updated 22 Oct 2026
Debian forkyforky · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:4.6p1-1Debian Security Tracker ↗Source updated 22 Oct 2026
Debian sidsid · sourceopensshVendor fix publishedDebian records a fixed source-package version for this release.1:4.6p1-1Debian Security Tracker ↗Source updated 22 Oct 2026
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2006-5036

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Mitigation available
01

What, why and how

Signal handler race condition in OpenSSH before 4.4 allows remote attackers to cause a denial of service (crash), and possibly execute arbitrary code if GSSAPI authentication is enabled, via unspecified vectors that lead to a double-free.

What

Signal handler race condition in OpenSSH before 4.4 allows remote attackers to cause a denial of service (crash), and possibly execute arbitrary code if GSSAPI authentication is enabled, via unspecified vectors that lead to a double-free.

Why

The product calls free() twice on the same memory address.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

Signal handler race condition in OpenSSH before 4.4 allows remote attackers to cause a denial of service (crash), and possibly execute arbitrary code if GSSAPI authentication is enabled, via unspecified vectors that lead to a double-free.

Why

The product calls free() twice on the same memory address.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Double Free → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-415 ↗

CWE-415: Double Free. The product calls free() twice on the same memory address.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionDenial of serviceCWE-415
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

NCSC-NL · Dutch · NCSC-2024-0362Kwetsbaarheden verholpen in Siemens producten

De kwetsbaarheden stellen een kwaadwillende mogelijk in staat aanvallen uit te voeren die kunnen leiden tot de volgende categorieën schade: - Denial-of-Service (DoS) - Manipulatie van gegevens - Omzeilen van een beveiligingsmaatregel - Omzeilen van authenticatie - (Remote) code execution (Administrator/Root rechten) - (Remote) code execution (Gebruikersrechten) - Toegang tot systeemgegevens - Verhoogde gebruikersrechten De kwaadwillende heeft hiervoor toegang nodig tot de productieomgeving. Het is goed gebruik een dergelijke omgeving niet publiek toegankelijk te hebben.

Official advisory ↗
NCSC-NL · Dutch · NCSC-2024-0272Kwetsbaarheid verholpen in OpenSSH

De kwetsbaarheid stelt een kwaadwillende in staat om zonder voorafgaande authenticatie willekeurige code uit te voeren met rechten van het sshd-proces. Het is niet uit te sluiten dat het ssh-proces met verhoogde rechten actief is, waardoor het mogelijk is dat de kwaadwillende code kan uitvoeren met rechten tot aan root. De kwetsbaarheid bevindt zich in een beperkt aantal versies. Versies van OpenSSH 8.5p1 en hoger, tot 9.7p1 zijn kwetsbaar, en versies tot aan 4.4p1, welke niet meer ondersteund worden. Versies tussen 4.4p1 en 8.5p1 zijn niet kwetsbaar. Dit komt omdat de kwetsbaarheid een regressie is van de eerder verholpen kwetsbaarheid met kenmerk CVE-2006-5051, welke in versie 4.4p1 is verholpen, maar in versie 8.5p1 herintroduceerd is. Daadwerkelijk misbruik is bijzonder ingewikkeld. Een kwaadwillende moet voor langere tijd connectiepogingen onderhouden. In een laboratoriumopstelling van de onderzoekers vereiste dat verbindingen van 6-8 uur, op 32-bit systemen. Theoretisch is het mogelijk om de kwetsbaarheid te misbruiken op 64-bit gebaseerde systemen, maar dat is nog niet aangetoond. Actief, grootschalig misbruik is hiermee dus onwaarschijnlijk. Echter, vanwege de grote verspreiding en het brede gebruik van OpenSSH is het niet onaannemelijk dat bepaalde actoren, zoals de georganiseerde misdaad, ransomware-groepen of statelijke actoren, interesse in deze kwetsbaarheid krijgen en de energie investeren om werkende malware te bouwen. Systemen met een actieve sshd-service, bereikbaar vanaf internet lopen het grootste risico. SSH is een populair protocol om op afstand systemen te beheren. Het verdient echter de afweging of de ssh-poort (standaard TCP poort 22, maar afhankelijk van de eigen installatie) actief en bereikbaar dient te zijn vanaf publieke netwerken. Er is Proof-of-Concept-code (PoC) gepubliceerd die de kwetsbaarheid kan aantonen, indien aan bovengenoemde tijdsrestricties wordt voldaan. De PoC is toegespitst op een specifieke distro, hetgeen aannemelijk maakt dat de PoC niet zondermeer generiek en grootschalig inzetbaar te maken is, zonder substantiële investering in resources. Door de lange benodigde tijd, in combinatie met het gegeven dat de code voor een specifiek doelwit geschikt gemaakt moet worden, is grootschalig misbruik niet aannemelijk. Het publiceren van de PoC toont wel aan dat de kwetsbaarheid de aandacht heeft van onderzoekers, en daarmee ook eventuele kwaadwillenden.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Mitigation available
Affected
n/a
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
De ontwikkelaars hebben een nieuwe versie van OpenSSH uitgebracht, OpenSSH 9.8/9.8p1. Eigenaars van systemen waarvan de SSH software in eigen beheer is kunnen de broncode downloaden en compileren. Leveranciers van Linux-distro's en systemen waarin OpenSSH in de firmware is geïmplementeerd zullen deze broncode moeten verwerken in nieuwe releases van distributie-packages of nieuwe firmware. Houd hiervoor de communicatie van uw leverancier in de gaten. Indien upgrades op korte termijn niet in te zetten zijn, kan als workaround in de sshd-configuratie de variabele 'LoginGraceTime' op 0 gezet worden. Hiermee wordt de tijd waarin een loginpoging mag 'wachten' op nul gezet, waardoor misbruik van de kwetsbaarheid niet mogelijk is. De consequentie van deze maatregel is echter wel dat het sshd-proces gevoelig gaat worden voor een Denial-of-Service. Het NCSC adviseert hier een eigen risico-afweging te maken, waarbij in de afweging meegenomen moet worden of het in eerste instantie noodzakelijk is dat de ssh-service in kwestie publiek toegankelijk moet zijn. Ook adviseert het NCSC om monitoring toe te passen op in gebruik zijnde SSH-services met een publieke toegang, en in de gaten te houden of herhaaldelijk sessies worden opgebouwd die uit hun gracetime lopen, de tijd waarin een login afgerond dient te zijn. Het NCSC houdt de ontwikkelingen in de gaten en werkt dit beveiligingsadvies bij wanneer relevante ontwikkelingen zich voordoen. Zie verder bijgevoegde referenties voor meer informatie.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 27 Sept 2006 · Last source change 7 Aug 2024, 19:32 UTC · CWE-415 · Double Free

CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-13
European sourceENISA EUVD · EUVD-2006-5036
Product sourceUnavailable
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment

Missing structured fields: affected product. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2006-5036 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2006-5036"}
    ENISA EUVD ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: secunia.com/22158; added vendor advisory: secunia.com/22173; removed vendor advisory: debian.org/dsa-1189; removed vendor advisory: debian.org/dsa-1212; 15 further additions; 11 further removals.
    Before
    vendor advisory: debian.org/dsa-1189 · vendor advisory: debian.org/dsa-1212 · vendor advisory: lists.apple.com/msg00002.html · 10 more references
    After
    vendor advisory: secunia.com/22158 · vendor advisory: secunia.com/22173 · vendor advisory: secunia.com/22183 · 14 more references
    secunia.com ↗
  3. SeveritySeverity changed from Unknown to High.
    Before
    Unknown
    After
    High
    NIST NVD ↗
  4. CVSS scoreCVSS score changed from not recorded to 8.1 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).
    Before
    not recorded
    After
    8.1 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)
    NIST NVD ↗
  5. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
  6. Remediation statusRemediation status changed from Awaiting fix to Mitigation available.
    Before
    Awaiting fix
    After
    Mitigation available
    NCSC-NL ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Remediation guidance recorded
ENISA EUVD · EUVD-2006-5036↗NCSC-NL remediation guidance↗Vendor advisory↗Vendor advisory↗Vendor advisory↗Vendor advisory↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2006-5051 · cve.blacktree.nl