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NVD / CVE Program· CNA redhat

CVE-2026-59849: Libssh: libssh: denial of service via automatic certificate authentication loop

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.43% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: libssh (AlmaLinux:10) 0.12.0-3.el10_2; libssh-config (AlmaLinux:10) 0.12.0-3.el10_2; libssh-devel (AlmaLinux:10) 0.12.0-3.el10_2.
  • Severity is disputed: the assigning authority (CNA) scores it 3.1, NVD 7.5.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to libssh (AlmaLinux:10) 0.12.0-3.el10_2; libssh-config (AlmaLinux:10) 0.12.0-3.el10_2; libssh-devel (AlmaLinux:10) 0.12.0-3.el10_2 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

A flaw was found in libssh. Logic errors in automatic certificate-based public key authentication can cause libssh clients to loop indefinitely when configured certificates are missing or repeatedly rejected by a server, leading to denial of service.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Jul 21, 2026
Updated
Nov 6, 2026
EPSS
0.4% · 38th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
7.5
CNA · redhat
3.1
4.4 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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-2026-59849

When you'll hear from us

  • when it enters CISA KEV
  • 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
libsshlibssh
redhathardened images
redhatenterprise linux
redhatenterprise linux for els
redhatenterprise linux for eus
redhatenterprise linux for ibm z systems
redhatenterprise linux for ibm z systems els
redhatenterprise linux for ibm z systems eus
redhatenterprise linux for power little endian
redhatenterprise linux for power little endian els
redhatenterprise linux for power little endian eus

Affected versions

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

  • libssh libssh0.11.0 and later · before 0.11.5
  • libssh libssh0.12.0
  • redhat enterprise linux10.0
  • redhat enterprise linux10.2
  • redhat enterprise linux for els10.2
  • redhat enterprise linux for eus10.2
  • redhat enterprise linux for ibm z systems10.0
  • redhat enterprise linux for ibm z systems10.2
  • redhat enterprise linux for ibm z systems els10.2
  • redhat enterprise linux for ibm z systems eus10.2
  • redhat enterprise linux for power little endian10.0
  • redhat enterprise linux for power little endian10.2
  • redhat enterprise linux for power little endian els10.2
  • redhat enterprise linux for power little endian eus10.2
  • redhat hardened imagesall versions

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • Red Hat Red Hat Enterprise Linux 10

    • 0:0.12.0-3.el10_2 and laternot affected · rpm

  • Red Hat Red Hat Enterprise Linux 8

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 9

    • all versionsunknown

  • Red Hat Red Hat Hardened Images

    • 0.12.1-4.hum1 and laternot affected · rpm

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:10libsshbefore 0.12.0-3.el10_20.12.0-3.el10_2
AlmaLinux:10libssh-configbefore 0.12.0-3.el10_20.12.0-3.el10_2
AlmaLinux:10libssh-develbefore 0.12.0-3.el10_20.12.0-3.el10_2
Alpine:v3.24libsshfrom 0.11.0 · before 0.12.1-r00.12.1-r0
Debian:13libsshbefore 0.11.5-0+deb13u10.11.5-0+deb13u1
Debian:14libsshbefore 0.12.1-10.12.1-1
openSUSE:Leap 16.0libsshbefore 0.11.5-160000.1.10.11.5-160000.1.1
openSUSE:Tumbleweedlibsshbefore 0.11.5-1.20.11.5-1.2
Red Hat:enterprise_linux:10.2libsshbefore 0:0.12.0-3.el10_20:0.12.0-3.el10_2
Red Hat:enterprise_linux:10.2libssh-configbefore 0:0.12.0-3.el10_20:0.12.0-3.el10_2
Red Hat:enterprise_linux:10.2libssh-debuginfobefore 0:0.12.0-3.el10_20:0.12.0-3.el10_2
Red Hat:enterprise_linux:10.2libssh-debugsourcebefore 0:0.12.0-3.el10_20:0.12.0-3.el10_2
Red Hat:enterprise_linux:10.2libssh-develbefore 0:0.12.0-3.el10_20:0.12.0-3.el10_2
Red Hat:hummingbird:1libsshbefore 0:0.12.1-4.hum10:0.12.1-4.hum1
Red Hat:hummingbird:1libssh-configbefore 0:0.12.1-4.hum10:0.12.1-4.hum1
Red Hat:hummingbird:1libssh-develbefore 0:0.12.1-4.hum10:0.12.1-4.hum1
Rocky Linux:10libsshbefore 0:0.12.0-3.el10_20:0.12.0-3.el10_2
SUSE:Linux Micro 6.2libsshbefore 0.11.5-160000.1.10.11.5-160000.1.1

Same product

libssh: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-10933A vulnerability was found in libssh's server-side state machine before versions 0.7.6 and 0.8.4.
    64This week
  • CVE-2019-14889A flaw was found with the libssh API function ssh_scp_new() in versions before 0.9.3 and before 0.8.8.
    36Monitor
  • CVE-2026-59851Libssh: libssh: authentication bypass via missing gssapi principal check
    35Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-59848Jul 21, 2026 · Libssh: libssh: denial of service via sftp responses with unknown request ids
    21Monitor
  • ← EarlierCVE-2026-59850Jul 21, 2026 · Libssh: libssh: use-after-free via data callbacks on closed channels
    30Monitor
  • ← EarlierCVE-2026-59842Jul 21, 2026 · Libssh: libssh: information disclosure via short gssapi curve25519 public key
    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:libssh0.12.0-3.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:libssh-config0.12.0-3.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:libssh-devel0.12.0-3.el10_2 · AlmaLinux:10Package registry (OSV)
alpine:libssh0.12.1-r0 · Alpine:v3.24Package registry (OSV)
debian:libssh0.11.5-0+deb13u1 · Debian:13Package registry (OSV)
opensuse:libssh0.11.5-1.2 · openSUSE:TumbleweedPackage registry (OSV)
red hat:libssh0:0.12.1-4.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:libssh-config0:0.12.1-4.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:libssh-debuginfo0:0.12.0-3.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:libssh-debugsource0:0.12.0-3.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:libssh-devel0:0.12.0-3.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:libssh-devel0:0.12.1-4.hum1 · Red Hat:hummingbird:1Package registry (OSV)
rocky linux:libssh0:0.12.0-3.el10_2 · Rocky Linux:10Package registry (OSV)
suse:libssh0.11.5-160000.1.1 · SUSE:Linux Micro 6.2Package 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

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

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-598430 days apartLibssh: libssh: denial of service via zero advertised channel packet size
    26Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

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

Weakness class (CWE)

CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')

CVSS vector

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

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

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

All records