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

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
36th
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. 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, 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 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.

The score's inputs: 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

November 10, 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

Patch Availability(3)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibssh2-1-dev (1.10.0-3ubuntu0.1) @ jammy2026-11-03ubuntu
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

(8 across 8 ecosystems)
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r3: fixed in 1.11.1-r3
—
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r3: fixed in 1.11.1-r3
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r4: fixed in 1.11.1-r4
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
libssh2—
  • every version up to 1.11.1-r4: fixed in 1.11.1-r4
—
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

(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 15× in last 7d / 44× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 397 rows 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 297 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

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

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 libssh2_publickey_list_fetch(), the version…
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 November 10, 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 (36th 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.

Dependency Blast Radius

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