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.
CVE-2025-26466
“▲” beside the score: it is higher than NVD's CVSS score.
Score elevated to 6.4 because EPSS predicted 39% probability of exploitation within the next 30 days (98th percentile of EPSS-scored CVEs) when EchelonGraph scored this CVE. NVD baseline CVSS 5.9 retained for reference. Confidence: see factors.
Also known asEUVD-2025-5920 (ENISA EUVD) · GHSA-m92w-x6j2-5gc5 (GitHub Security Advisories)Source: ENISA EUVD
- Public exploit or proof-of-concept code is available
A fix is available — apply it.
- CVSS v3
- 5.9
- EG Score
- 6.4MEDIUMhigh confidence
- EG Risk
- 43EG Risk 43/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity59% × 45%Impact severity (EG Severity): CVSS 5.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation40% × 40%EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 39%
- EPSS %ILE
- 98th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (6.4): severity, escalated by confirmed exploitation. This CVE's 6.4 is EPSS's lift toward 9.0 from its impact severity (EG Severity, CVSS 5.9 MEDIUM): a likelihood of exploitation, not impact.
- EG Severity
- 5.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 39% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
February 28, 2025
Last Modified
October 21, 2026
Advisory Details (10)
Auto-updated Jun 25, 20261237041 – (CVE-2025-26466) VUL-0: CVE-2025-26466: openssh,openssh8.4: DoS attack against OpenSSH's client and server
https://bugzilla.suse.com/show_bug.cgi?id=1237041Full Disclosure: APPLE-SA-05-12-2025-4 macOS Sonoma 14.7.6
http://seclists.org/fulldisclosure/2025/May/8Full Disclosure: APPLE-SA-05-12-2025-3 macOS Sequoia 15.5
http://seclists.org/fulldisclosure/2025/May/7Full Disclosure: Re: MitM attack against OpenSSH's VerifyHostKeyDNS-enabled client
http://seclists.org/fulldisclosure/2025/Feb/18oss-sec: MitM attack against OpenSSH's VerifyHostKeyDNS-enabled client
https://seclists.org/oss-sec/2025/q1/1442345043 – (CVE-2025-26466) CVE-2025-26466 openssh: Denial-of-service in OpenSSH
https://bugzilla.redhat.com/show_bug.cgi?id=2345043cve-details
https://access.redhat.com/security/cve/CVE-2025-26466Vendor Advisories for CVE-2025-26466(4)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- CVE-2025-26466Microsoft Security Response Center (MSRC)High
Openssh: denial-of-service in openssh
- RHSA-2025:6993Red Hat Product SecurityMedium
Red Hat Security Advisory: openssh security update
- RHBA-2025:6305Red Hat Product SecurityMedium
Red Hat Bug Fix Advisory: openssh bug fix and enhancement update
- GHSA-m92w-x6j2-5gc5GitHub Security AdvisoriesMedium
A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong...
Patch Availability(3)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| ubuntu | ssh-askpass-gnome (1:8.9p1-3ubuntu0.11) @ jammy | 2026-10-21 | ubuntu |
| redhat | openssh-0:9.9p1-7.el10_0 | 2025-05-13 | redhat |
| redhat | openssh-0:8.7p1-45.el9 | 2025-05-13 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(8 across 8 ecosystems)
Alpine:v3.19(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Alpine:v3.20(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Alpine:v3.21(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Alpine:v3.22(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Alpine:v3.23(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Alpine:v3.24(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| openssh | — |
| — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(1)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Data Freshness Timeline
(refreshed 5× in last 7d / 57× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 96 of 185 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 100 are merged into the row they repeat. The 89 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-31 16:30 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-30 16:32 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-29 16:31 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-28 16:30 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-27 16:30 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-26 16:29 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-25 16:34 UTCEG score recompute▼ 0.10
- 2026-10-25 16:34 UTCVendor advisory
- 2026-10-25 16:33 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-25 16:31 UTCEPSS rescoreEPSS 39% · 98th percentile
- 2026-10-24 16:30 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-23 16:30 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-22 16:32 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-21 17:28 UTCVendor advisory
- 2026-10-21 17:28 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-21 17:13 UTCEG score recompute
- 2026-10-21 17:13 UTCVendor advisory
- 2026-10-21 17:13 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-21 16:30 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-20 16:31 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-19 16:30 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-18 05:42 UTCEG score recompute
- 2026-10-17 16:32 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-16 16:38 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-15 16:30 UTCEPSS rescoreEPSS 41% · 98th percentile
Show 71 moreShow fewer
- 2026-10-15 02:52 UTCVendor advisory
- 2026-10-15 02:52 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-15 02:00 UTCEG score recompute
- 2026-10-15 02:00 UTCVendor advisory
- 2026-10-15 01:59 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-14 16:31 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-13 16:32 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-12 17:15 UTCEG score recompute
- 2026-10-11 20:47 UTCEG score recompute
- 2026-10-11 18:57 UTCEG score recompute
- 2026-10-11 15:36 UTCEG score recompute
- 2026-10-11 13:47 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-10 19:59 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-09 20:06 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-08 22:24 UTCVendor advisory
- 2026-10-08 22:24 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-08 22:13 UTCEG score recompute
- 2026-10-08 22:13 UTCVendor advisory
- 2026-10-08 22:13 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-08 17:09 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-08 12:26 UTCVendor advisory
- 2026-10-08 12:26 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-08 12:07 UTCVendor advisory
- 2026-10-08 12:07 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-08 09:18 UTCVendor advisory
- 2026-10-08 09:18 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-08 08:57 UTCEG score recompute▲ 0.10
- 2026-10-08 08:57 UTCVendor advisory
- 2026-10-08 08:57 UTCGHSA enrichmentGHSA-m92w-x6j2-5gc5 · GitHub CVSS 5.9
- 2026-10-07 23:46 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-06 15:16 UTCEPSS rescoreEPSS 41% · 98th percentile
- 2026-10-05 17:42 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-10-03 14:24 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-10-02 21:40 UTCOSV refresh
- 2026-10-02 16:26 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-10-01 19:48 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-30 15:02 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-28 13:50 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-26 00:24 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-24 14:02 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-23 13:46 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-22 14:47 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-18 19:27 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-16 14:06 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-16 05:13 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-15 03:09 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-13 19:09 UTCOSV refresh
- 2026-09-12 15:00 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-11 09:35 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-10 09:33 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-08 21:59 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-06 13:46 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-05 15:28 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-04 05:05 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-02 14:11 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-09-01 04:38 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-30 19:16 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-30 01:21 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-28 21:40 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-27 14:24 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-25 20:39 UTCOSV refresh
- 2026-08-25 13:47 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-21 23:48 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-20 22:54 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-18 13:47 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-17 13:46 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-16 14:55 UTCEPSS rescoreEPSS 40% · 98th percentile
- 2026-08-16 02:13 UTCEPSS rescoreEPSS 40% · 98th percentile
Publicly available exploits
(1 reference)Public exploit code is referenced for this CVE (1 GitHub PoC). Defenders should treat patch urgency accordingly.
- GitHub PoCrxerium/CVE-2025-26466Published Feb 18, 2025
The OpenSSH client and server are vulnerable to a pre-authentication DoS attack between versions 9.5p1 to 9.9p1 (inclusive) that causes memory and CPU consumption
Open source ↗
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownAlpine:v3.19:openssh
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- CVE-2018-15473NVD 5.3EG 9.0EPSS p100CRITICAL
- CVE-2020-15778NVD 7.4EG 7.8EPSS p96HIGH
- CVE-2016-10012EG 7.8HIGH
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- CVE-2016-10009NVD 7.3EG 7.5EPSS p99HIGH
- CVE-2021-28041EG 7.1HIGH
- CVE-2021-41617EG 7.0HIGH
Frequently asked(5)
What is CVE-2025-26466?
When was CVE-2025-26466 made public?
Is CVE-2025-26466 actively exploited?
What is the CVSS score of CVE-2025-26466?
How do I remediate CVE-2025-26466?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2025-26466
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