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Full vulnerability report · 2026
CVE-2026-7598High confidence

libssh2 userauth.c userauth_password integer overflow

n/a · libssh2

6.9MediumCVSS 4.0
Recommended action
Within 7 days

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Distribution package intelligence

Ubuntu vendor package status

Canonical’s release and source-package findings are shown separately from local repository availability.

1 package state
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.

Ubuntu releaseSource packageVendor stateFixed versionEvidence
Ubuntu 24.04 LTSnoble · standard archivelibssh2Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.1.11.0-4.1ubuntu0.24.04.1Canonical record ↗Source updated 8 Sept 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-7598 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitylibssh2: integer overflow via large username or password arguments
5 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • libssh2 as a component of Red Hat Enterprise Linux 6
  • libssh2-devel as a component of Red Hat Enterprise Linux 6
  • libssh2-docs as a component of Red Hat Enterprise Linux 6
  • libssh2.src as a component of Red Hat Enterprise Linux 6
  • rhtpa/rhtpa-trustification-service-rhel9 as a component of Red Hat Trusted Profile Analyzer
Summary
A flaw was found in the libssh2 library. A remote attacker can exploit an integer overflow vulnerability in the `userauth_password` function by manipulating the `username_len` or `password_len` arguments and cause a heap-based buffer overflow. This leads to a crash to the application linked to the library and potentially allows arbitrary code execution.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Optional official sources

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

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

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-2026-26722

No EUVD known-exploited evidence

A security vulnerability has been detected in libssh2 up to 1.11.1. The impacted element is the function userauth_password of the file src/userauth.c. Such manipulation of the argument username_len/password_len leads to integer overflow. The attack may be launched remotely. The name of the patch is 256d04b60d80bf1190e96b0ad1e91b2174d744b1. A patch should be applied to remediate this issue.

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
6.9 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

A security vulnerability has been detected in libssh2 up to 1.11.1. The impacted element is the function userauth_password of the file src/userauth.c. Such manipulation of the argument username_len/password_len leads to integer overflow. The attack may be launched remotely. The name of the patch is 256d04b60d80bf1190e96b0ad1e91b2174d744b1. A patch should be applied to remediate this issue.

What

A security vulnerability has been detected in libssh2 up to 1.11.1. The impacted element is the function userauth_password of the file src/userauth.c. Such manipulation of the argument username_len/password_len leads to integer overflow. The attack may be launched remotely. The name of the patch is 256d04b60d80bf1190e96b0ad1e91b2174d744b1. A patch should be applied to remediate this issue.

Why

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

A security vulnerability has been detected in libssh2 up to 1.11.1. The impacted element is the function userauth_password of the file src/userauth.c. Such manipulation of the argument username_len/password_len leads to integer overflow. The attack may be launched remotely. The name of the patch is 256d04b60d80bf1190e96b0ad1e91b2174d744b1. A patch should be applied to remediate this issue.

Why

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

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.
Reference recorded

CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.

Likely attack path
a network path → Integer Overflow or Wraparound → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-190 ↗

CWE-190: Integer Overflow or Wraparound. The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCLowVulnerable-system confidentiality: A successful attack can cause a limited loss.VILowVulnerable-system integrity: A successful attack can cause a limited loss.VALowVulnerable-system availability: A successful attack can cause a limited loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-190Public exploit reference
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-26722Official EUVD mapping

A security vulnerability has been detected in libssh2 up to 1.11.1. The impacted element is the function userauth_password of the file src/userauth.c. Such manipulation of the argument username_len/password_len leads to integer overflow. The attack may be launched remotely. The name of the patch is 256d04b60d80bf1190e96b0ad1e91b2174d744b1. A patch should be applied to remediate this issue.

Official EUVD record
BSI · German · WID-SEC-W-2026-1332libssh2: Schwachstelle ermöglicht Denial of Service

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in libssh2 ausnutzen, um einen Denial of Service Angriff durchzuführen.

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.
Patch available
Affected
libssh2 as a component of Red Hat Enterprise Linux 6; libssh2-devel as a component of Red Hat Enterprise Linux 6; libssh2-docs as a component of Red Hat Enterprise Linux 6; libssh2.src as a component of Red Hat Enterprise Linux 6; rhtpa/rhtpa-trustification-service-rhel9 as a component of Red Hat Trusted Profile Analyzer
Fixed
libssh2-0:1.8.0-4.el7_9.2.i686 as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.ppc as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.ppc64 as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.ppc64le as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.s390 as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.s390x as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.src as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-0:1.8.0-4.el7_9.2.x86_64 as a component of Red Hat Enterprise Linux Server (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.i686 as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.ppc as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.ppc64 as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.ppc64le as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.s390 as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.s390x as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-devel-0:1.8.0-4.el7_9.2.x86_64 as a component of Red Hat Enterprise Linux Server Optional (v. 7 ELS); libssh2-main@aarch64 as a component of Red Hat Hardened Images; libssh2-main@noarch as a component of Red Hat Hardened Images; libssh2-main@src as a component of Red Hat Hardened Images; libssh2-main@x86_64 as a component of Red Hat Hardened Images; rust-main@aarch64 as a component of Red Hat Hardened Images; rust-main@noarch as a component of Red Hat Hardened Images; rust-main@src as a component of Red Hat Hardened Images; rust-main@x86_64 as a component of Red Hat Hardened Images
Action
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
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 1 May 2026 · Last source change 1 Sept 2026, 12:04 UTC · CWE-190 · Integer Overflow or Wraparound

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-26722
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →
  1. Vendor guidanceAuthoritative vendor guidance changed from authoritative remediation link · patch, vendor advisory to authoritative remediation link · patch.
    Before
    authoritative remediation link · patch, vendor advisory
    After
    authoritative remediation link · patch
    cna@vuldb.com ↗
  2. Vendor guidanceAuthoritative vendor guidance changed from authoritative remediation link · patch to authoritative remediation link · patch, vendor advisory.
    Before
    authoritative remediation link · patch
    After
    authoritative remediation link · patch, vendor advisory
    cna@vuldb.com ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-26722↗Vendor CSAF · Red Hat Product Security↗CISA Vulnrichment SSVC evidence↗Patch or update reference↗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-2026-7598 · cve.blacktree.nl