CVE-2026-66034

HIGHPre-NVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-07-24. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this week

Also known asEUVD-2026-48721 (ENISA EUVD) · GHSA-6h6q-9mwg-r6x7 (GitHub Security Advisories)Source: ENISA EUVD

7.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
34
EG Risk 34/100

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)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
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 none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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
0.4%
EPSS %ILE
34th
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 (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-27). 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: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: 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 none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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

July 24, 2026

Last Modified

July 30, 2026

Advisory Details (3)

Auto-updated Jul 24, 2026
Patch available. Sources: github_pr, github_commit.
Web page

libssh2 Heap Out-of-Bounds Read via publickey subsystem | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-heap-out-of-bounds-read-via-publickey-subsystem
GitHub commit

commit a13bb6c773f0 (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit a13bb6c773f0 — awaiting tagged release

https://github.com/libssh2/libssh2/commit/a13bb6c773f0d55ad1628cede57e99803cd898d9
GitHub pull request

publickey: fix potential OOB read in `libssh2_publickey_list_fetch()`

Upstream fix in progress (PR #2202 · libssh2/libssh2, state=closed)

https://github.com/libssh2/libssh2/pull/2202

Vendor Advisories for CVE-2026-66034(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibssh2-1-dev (1.5.0-2ubuntu0.1+esm3) @ xenial2026-10-27ubuntu
redhatlibssh2-0:1.8.0-4.el7_9.22026-08-31redhat
redhatlibssh2-main-1.11.1-10.2.hum12026-07-27redhat

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

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.10.0-1 ... 1.9.0-3 (20 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.10.0-3
  • every version up to 1.10.0-3+deb12u1: fixed in 1.10.0-3+deb12u1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.11.1-1, 1.11.1-1+deb13u1
  • every version up to 1.11.1-1+deb13u2: fixed in 1.11.1-1+deb13u2
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.11.1-1, 1.11.1-2, 1.11.1-3, 1.11.1-4
  • every version up to 1.11.1-5: fixed in 1.11.1-5
—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(2)

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 11× in last 7d / 51× 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 100 of 369 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. None are among the latest 100 rows. The 269 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  2. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  3. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  4. 2026-10-27 19:05 UTCEG score recompute
  5. 2026-10-27 19:05 UTCVendor advisory
  6. 2026-10-27 19:04 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  7. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  8. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  9. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  10. 2026-10-25 14:11 UTCEG score recompute
  11. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  12. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  13. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  14. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  15. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  16. 2026-10-20 09:08 UTCEG score recompute
  17. 2026-10-20 09:08 UTCVendor advisory
  18. 2026-10-20 09:08 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  19. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  20. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  21. 2026-10-18 03:21 UTCEG score recompute
  22. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  23. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  24. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
Show 75 more
  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  2. 2026-10-13 11:02 UTCEG score recompute
  3. 2026-10-13 11:02 UTCVendor advisory
  4. 2026-10-13 11:01 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  5. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  6. 2026-10-12 15:46 UTCEG score recompute
  7. 2026-10-11 19:31 UTCEG score recompute
  8. 2026-10-11 16:46 UTCEG score recompute
  9. 2026-10-11 14:07 UTCEG score recompute
  10. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  11. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  12. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  13. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  18. 2026-10-04 07:42 UTCEG score recompute
  19. 2026-10-04 07:42 UTCVendor advisory
  20. 2026-10-04 07:42 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  21. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  22. 2026-10-03 03:18 UTCEG score recompute
  23. 2026-10-03 03:18 UTCVendor advisory
  24. 2026-10-03 03:18 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  25. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  26. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  27. 2026-10-01 05:59 UTCEG score recompute
  28. 2026-10-01 05:59 UTCVendor advisory
  29. 2026-10-01 05:59 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  30. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  31. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  32. 2026-09-28 04:27 UTCEG score recompute
  33. 2026-09-28 04:27 UTCVendor advisory
  34. 2026-09-28 04:27 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  35. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  36. 2026-09-25 10:06 UTCEG score recompute
  37. 2026-09-25 10:06 UTCVendor advisory
  38. 2026-09-25 10:06 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  39. 2026-09-24 09:45 UTCVendor advisory
  40. 2026-09-24 09:45 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  41. 2026-09-23 22:17 UTCEG score recompute
  42. 2026-09-23 22:17 UTCVendor advisory
  43. 2026-09-23 22:17 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  44. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  45. 2026-09-23 09:38 UTCVendor advisory
  46. 2026-09-23 09:38 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  47. 2026-09-22 22:11 UTCEG score recompute
  48. 2026-09-22 22:11 UTCVendor advisory
  49. 2026-09-22 22:10 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  50. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  51. 2026-09-20 01:39 UTCEG score recompute
  52. 2026-09-20 01:39 UTCVendor advisory
  53. 2026-09-20 01:39 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  54. 2026-09-18 22:28 UTCEG score recompute
  55. 2026-09-18 22:28 UTCVendor advisory
  56. 2026-09-18 22:28 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  57. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  58. 2026-09-18 02:58 UTCEG score recompute
  59. 2026-09-18 02:58 UTCVendor advisory
  60. 2026-09-18 02:58 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  61. 2026-09-17 01:58 UTCEG score recompute
  62. 2026-09-17 01:58 UTCVendor advisory
  63. 2026-09-17 01:58 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  64. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  65. 2026-09-16 06:39 UTCEG score recompute
  66. 2026-09-16 06:39 UTCVendor advisory
  67. 2026-09-16 06:39 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  68. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  69. 2026-09-15 09:36 UTCEG score recompute
  70. 2026-09-15 09:36 UTCVendor advisory
  71. 2026-09-15 09:36 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  72. 2026-09-14 16:06 UTCVendor advisory
  73. 2026-09-14 16:06 UTCGHSA enrichmentGHSA-6h6q-9mwg-r6x7 · GitHub severity HIGH · GitHub CVSS 7.5
  74. 2026-09-14 02:56 UTCEG score recompute
  75. 2026-09-14 02:56 UTCVendor advisory

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-66034?
CVE-2026-66034 is a high-severity vulnerability; its CVE record was published on July 24, 2026. libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2publickeylistfetch(), the version 1…
When was CVE-2026-66034 made public?
CVE-2026-66034 was made public on July 4, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on July 24, 2026. EchelonGraph's copy of the record carries a last-modified date of July 30, 2026; the record at its source may have been updated since.
Is CVE-2026-66034 actively exploited?
CVE-2026-66034 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (34th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66034?
CVE-2026-66034 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-66034?
A fix for CVE-2026-66034 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-66034 are linked in the Vendor Advisories panel on this page.

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