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In sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF > 0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code execution. 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Please update the affected package as soon as possible."}],"x_generator":{"engine":"cvelib 1.8.0"},"x_redhatCweChain":"CWE-191: Integer Underflow (Wrap or Wraparound)"}},"cveMetadata":{"assignerOrgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","assignerShortName":"redhat","cveId":"CVE-2026-18355","datePublished":"2026-09-07T14:14:43.759Z","dateReserved":"2026-07-30T07:37:32.170Z","dateUpdated":"2026-09-08T07:56:53.291Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-07 15:17:30","lastModifiedDate":"2026-09-08 08:17:10","problem_types":["CWE-191","CWE-191 Integer Underflow (Wrap or Wraparound)"],"metrics":{"cvssMetricV31":[{"source":"secalert@redhat.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.6,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"18355","Ordinal":"1","Title":"389-ds-base: 389-ds-base: heap buffer overflow via sasl wrapped-","CVE":"CVE-2026-18355","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"18355","Ordinal":"1","NoteData":"A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF > 0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code execution. This flaw is distinct from CVE-2026-11774, whose fix only guards against upper-bound overflow.","Type":"Description","Title":"389-ds-base: 389-ds-base: heap buffer overflow via sasl wrapped-"}]}}}