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NVD / CVE Program· CNA redhat

CVE-2025-26466: Openssh: denial-of-service in openssh

Noroxi assessment

Priority: Monitor (action score 35/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 38.6% (FIRST EPSS); higher than 98.5% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: azl3 openssh 9.8p1-3 on Azure Linux 3.0 9.8p1-3; azl3 openssh 9.8p1-4 on Azure Linux 3.0 9.8p1-3.

Low priority for now. Upgrade to azl3 openssh 9.8p1-3 on Azure Linux 3.0 9.8p1-3; azl3 openssh 9.8p1-4 on Azure Linux 3.0 9.8p1-3 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 the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack.

MediumCVSS 5.9 · v3.1—Proof of concept Fix available
Published
Feb 28, 2025
Updated
Oct 21, 2026
EPSS
38.6% · 98th percentile

Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
23 / 40 · 5.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
12 / 30 · 38.6%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.9
CNA · redhat
5.9
agree

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
  • Proof of concept exists, no weaponized module
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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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
openbsdopenssh
canonicalubuntu linux
debiandebian linux

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Affected versions

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

  • canonical ubuntu linux24.04
  • canonical ubuntu linux24.10
  • debian debian linux11.0
  • debian debian linux12.0
  • debian debian linux13.0
  • openbsd openssh9.5
  • openbsd openssh9.6
  • openbsd openssh9.7
  • openbsd openssh9.8
  • openbsd openssh9.9

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

    • 0:9.9p1-7.el10_0 and laternot affected · rpm

  • Red Hat Red Hat Enterprise Linux 6

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 7

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 8

    • all versionsunknown

  • Red Hat Red Hat Enterprise Linux 9

    • 0:8.7p1-45.el9 and laternot affected · rpm
    • 0:8.7p1-45.el9 and laternot affected · rpm

  • Red Hat Red Hat OpenShift Container Platform 4

    • all versionsunknown
    • all versionsunknown

  • www.openssh.com/ OpenSSH

    • 9.5p1 and later · up to and including 9.9p1affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Alpine:v3.19opensshbefore 9.6_p1-r29.6_p1-r2
Alpine:v3.20opensshbefore 9.7_p1-r59.7_p1-r5
Alpine:v3.21opensshbefore 9.9_p2-r09.9_p2-r0
Debian:13opensshbefore 1:9.9p2-11:9.9p2-1
openSUSE:Leap 15.6opensshbefore 9.6p1-150600.6.15.29.6p1-150600.6.15.2
openSUSE:Leap 15.6openssh-askpass-gnomebefore 9.6p1-150600.6.15.19.6p1-150600.6.15.1
openSUSE:Tumbleweedopensshbefore 9.9p2-1.19.9p2-1.1
Red Hat:enterprise_linux:10.0opensshbefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-askpassbefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-askpass-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-clientsbefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-clients-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-debugsourcebefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-keycatbefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-keycat-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-keysignbefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-keysign-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-serverbefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-server-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:10.0openssh-sk-dummy-debuginfobefore 0:9.9p1-7.el10_00:9.9p1-7.el10_0
Red Hat:enterprise_linux:9::appstreamopenssh-askpassbefore 0:8.7p1-45.el90:8.7p1-45.el9
Red Hat:enterprise_linux:9::appstreamopenssh-askpass-debuginfobefore 0:8.7p1-45.el90:8.7p1-45.el9
Red Hat:enterprise_linux:9::appstreamopenssh-clients-debuginfobefore 0:8.7p1-45.el90:8.7p1-45.el9

+15

Same product

openbsd: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-38408The PKCS#11 feature in ssh-agent in OpenSSH before 9.3p2 has an insufficiently trustworthy search path, leading to remote code execution if
    63This week
  • CVE-2018-15473OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after
    60This week
  • CVE-2016-6210sshd in OpenSSH before 7.3, when SHA256 or SHA512 are used for user password hashing, uses BLOWFISH hashing on a static password when the us
    60This week

Published before and after this one in the same product

  • ← EarlierCVE-2023-51767Dec 24, 2023 · OpenSSH through 10.0, when common types of DRAM are used, might allow row hammer attacks (for authentication bypass) because the integer val
    28Monitor
  • ← EarlierCVE-2025-26465Feb 18, 2025 · Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled
    29Monitor
  • Later →CVE-2025-32728Apr 10, 2025 · In sshd in OpenSSH before 10.0, the DisableForwarding directive does not adhere to the documentation stating that it disables X11 and agent
    15Monitor

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
azl3 openssh 9.8p1-3 on Azure Linux 3.09.8p1-3 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 openssh 9.8p1-4 on Azure Linux 3.09.8p1-3 · CBL-Mariner ReleasesMicrosoft (MSRC)
alpine:openssh9.6_p1-r2 · Alpine:v3.19Package registry (OSV)
debian:openssh1:9.9p2-1 · Debian:13Package registry (OSV)
opensuse:openssh9.6p1-150600.6.15.2 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:openssh-askpass-gnome9.6p1-150600.6.15.1 · openSUSE:Leap 15.6Package registry (OSV)
red hat:openssh0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-askpass0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-askpass-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-clients0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-clients-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-debugsource0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-keycat-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-keysign0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-keysign-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-server-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
red hat:openssh-sk-dummy-debuginfo0:9.9p1-7.el10_0 · Red Hat:enterprise_linux:10.0Package registry (OSV)
suse:openssh9.6p1-150600.6.15.2 · SUSE:Linux Enterprise Module for Basesystem 15 SP6Package registry (OSV)
suse:openssh-askpass-gnome9.6p1-150600.6.15.1 · SUSE:Linux Enterprise Module for Desktop Applications 15 SP6Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×5

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:52025-02-18
Proof-of-concept repository on GitHubstars:12025-06-23
Proof-of-concept repository on GitHubstars:02026-04-02
Proof-of-concept repository on GitHubstars:02026-07-29
Proof-of-concept repository on GitHubstars:02026-10-09

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.

  1. First PoC-11 d
  2. Published
  3. TodayNov 3, 2026+613 d
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.

No credits in the CNA record.

Variant candidates

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

  • CVE-2026-60000495 days apartsshd in OpenSSH before 10.4 allows remote attackers to cause a denial of service (resource consumption from excessive authentication attempt
    30Monitor
  • CVE-2026-60001495 days apartsshd in OpenSSH before 10.4 does not always honor the minimum authentication delay.
    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).

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.
  • Special conditions such as timing or configuration are required.

If successful

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

Weakness class (CWE)

CWE-770 · Allocation of Resources Without Limits or Throttling

CVSS vector

CVSS:3.1/AV:N/AC:H/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.

Change log

  1. Fix✗ → ✓

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

References

Show all references (17 more)

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

All records