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CVE-2026-66035

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 o
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:3491d6ce927986d6f77b7a7d48443d9d604d1fc5bad8234f2cb11cfb251565ec
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cvss · 2 assertions

{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"HIGH","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":7.7,"baseSeverity":"HIGH","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"PASSIVE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpac…

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/metrics/0/cvssV4_0

{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"},"metric_type":"cvssV3_1"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/metrics/1/cvssV3_1

Affected products and versions

1 source assertion
{"defaultStatus":"affected","packageURL":"pkg:github/libssh2/libssh2","product":"libssh2","repo":"https://github.com/libssh2/libssh2","vendor":"libssh2","versions":[{"lessThanOrEqual":"1.11.1","status":"affected","version":"0","versionType":"semver"},{"status":"unaffected","version":"42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4","versionType":"git"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/affected/0

Provider-owned CVSS observations

2 source assertions
{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"HIGH","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":7.7,"baseSeverity":"HIGH","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"PASSIVE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpac…
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/metrics/0/cvssV4_0
{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/metrics/1/cvssV3_1

CWE assertions

1 source assertion
{"cweId":"CWE-122","description":"Heap-based Buffer Overflow","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/problemTypes/0/descriptions/0

Source references

3 source assertions
{"name":"Patch Commit","tags":["patch"],"url":"https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5eeb4"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/references/1
{"name":"Pull Request","tags":["issue-tracking","patch"],"url":"https://github.com/libssh2/libssh2/pull/2198"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/references/0
{"tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-cipher-negotiation"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:105775790a7b5fcb03a5c6e3bfff395b36c9612d0f360781fa4d606b62898282 · sha256:e2c6612f6ca110b7… · /containers/cna/references/2

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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