CVE-2026-66035

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 — 5 sources updated this week

Also known asEUVD-2026-48722 (ENISA EUVD) · GHSA-v6rf-8q4r-r495 (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: 0.5%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packet_length smaller than the cipher's block size during Encrypt-then-MAC cipher negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit glibc writes attacker-controlled bytes into an adjacent chunk's SIZE field, enabling tcache bin confusion, overlapping live objects, and function pointer overwrite during the session handshake before authentication.

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.
Exploitation0.5% × 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
0.5%
EPSS %ILE
40th
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
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-28). 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_commit, github_pr.
Web page

libssh2 Heap Buffer Overflow via ETM Cipher Negotiation | Advisories | VulnCheck

https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-cipher-negotiation
GitHub pull request

transport: fix potential heap overflow on ETM decrypt

Upstream fix in progress (PR #2198 · libssh2/libssh2, state=closed)

https://github.com/libssh2/libssh2/pull/2198
GitHub commit

commit 42e33d81577e (libssh2/libssh2)

Fix landed in libssh2/libssh2 commit 42e33d81577e — awaiting tagged release

https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4

Vendor Advisories for CVE-2026-66035(3)

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

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibssh2-1t64 (1.11.1-1ubuntu0.26.04.4) @ resolute2026-10-29ubuntu
redhatlibssh2-main-1.11.1-10.3.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

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libssh21.10.0-3 ... 1.11.1-5 (15 versions)
  • every version on: no fix on record
—
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(1)

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 12× in last 7d / 52× 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 364 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 264 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 0.5% · 40th percentile
  2. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  3. 2026-10-29 01:09 UTCEG score recompute
  4. 2026-10-29 01:09 UTCVendor advisory
  5. 2026-10-29 01:09 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  6. 2026-10-28 21:55 UTCOSV refresh
  7. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  9. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  11. 2026-10-25 14:11 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  13. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  14. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  15. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  16. 2026-10-21 03:53 UTCEG score recompute
  17. 2026-10-21 03:53 UTCVendor advisory
  18. 2026-10-21 03:53 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  19. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  20. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  21. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  22. 2026-10-18 03:21 UTCEG score recompute
  23. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  24. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  25. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
Show 75 more
  1. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  2. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  3. 2026-10-13 11:01 UTCEG score recompute
  4. 2026-10-13 11:01 UTCVendor advisory
  5. 2026-10-13 11:01 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  6. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  7. 2026-10-12 15:46 UTCEG score recompute
  8. 2026-10-11 19:31 UTCEG score recompute
  9. 2026-10-11 16:46 UTCEG score recompute
  10. 2026-10-11 14:07 UTCEG score recompute
  11. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  12. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  13. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  14. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  15. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  16. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  17. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  18. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  19. 2026-10-04 07:42 UTCEG score recompute
  20. 2026-10-04 07:42 UTCVendor advisory
  21. 2026-10-04 07:42 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  22. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  23. 2026-10-03 03:18 UTCEG score recompute
  24. 2026-10-03 03:18 UTCVendor advisory
  25. 2026-10-03 03:18 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  26. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  27. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  28. 2026-10-01 05:59 UTCEG score recompute
  29. 2026-10-01 05:59 UTCVendor advisory
  30. 2026-10-01 05:59 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  31. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  32. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  33. 2026-09-28 04:27 UTCEG score recompute
  34. 2026-09-28 04:27 UTCVendor advisory
  35. 2026-09-28 04:27 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  36. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  37. 2026-09-25 10:06 UTCEG score recompute
  38. 2026-09-25 10:06 UTCVendor advisory
  39. 2026-09-25 10:06 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  40. 2026-09-24 09:50 UTCVendor advisory
  41. 2026-09-24 09:50 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  42. 2026-09-23 22:17 UTCEG score recompute
  43. 2026-09-23 22:17 UTCVendor advisory
  44. 2026-09-23 22:17 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  45. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  46. 2026-09-23 09:43 UTCVendor advisory
  47. 2026-09-23 09:43 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  48. 2026-09-22 22:11 UTCEG score recompute
  49. 2026-09-22 22:11 UTCVendor advisory
  50. 2026-09-22 22:10 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  51. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  52. 2026-09-20 01:39 UTCEG score recompute
  53. 2026-09-20 01:39 UTCVendor advisory
  54. 2026-09-20 01:39 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  55. 2026-09-18 22:28 UTCEG score recompute
  56. 2026-09-18 22:28 UTCVendor advisory
  57. 2026-09-18 22:28 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  58. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  59. 2026-09-18 02:58 UTCEG score recompute
  60. 2026-09-18 02:58 UTCVendor advisory
  61. 2026-09-18 02:58 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  62. 2026-09-17 01:58 UTCEG score recompute
  63. 2026-09-17 01:58 UTCVendor advisory
  64. 2026-09-17 01:58 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  65. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  66. 2026-09-16 06:39 UTCEG score recompute
  67. 2026-09-16 06:39 UTCVendor advisory
  68. 2026-09-16 06:39 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  69. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 39th percentile
  70. 2026-09-15 09:35 UTCEG score recompute
  71. 2026-09-15 09:35 UTCVendor advisory
  72. 2026-09-15 09:35 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  73. 2026-09-14 16:06 UTCVendor advisory
  74. 2026-09-14 16:06 UTCGHSA enrichmentGHSA-v6rf-8q4r-r495 · GitHub severity HIGH · GitHub CVSS 7.5
  75. 2026-09-14 03:22 UTCEG score recompute

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Frequently asked(5)

What is CVE-2026-66035?
CVE-2026-66035 is a high-severity vulnerability; its CVE record was published on July 24, 2026. libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-MAC…
When was CVE-2026-66035 made public?
CVE-2026-66035 was made public on July 3, 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-2026-66035 actively exploited?
CVE-2026-66035 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66035?
CVE-2026-66035 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-2026-66035?
A fix for CVE-2026-66035 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-66035 are linked in the Vendor Advisories panel on this page.

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