{"id":"CVE-2018-1000159","aliases":["GHSA-cwh5-3cw7-4286","PYSEC-2018-31"],"url":"https://o3.security/vulnerability/CVE-2018-1000159","summary":"tlslite-ng off-by-one error on mac checking","details":"tlslite-ng version 0.7.3 and earlier, since commit d7b288316bca7bcdd082e6ccff5491e241305233 contains a CWE-354: Improper Validation of Integrity Check Value vulnerability in TLS implementation, tlslite/utils/constanttime.py: ct_check_cbc_mac_and_pad(); line \"end_pos = data_len - 1 - mac.digest_size\" that can result in an attacker manipulating the TLS ciphertext which will not be detected by receiving tlslite-ng. This attack appears to be exploitable via man in the middle on a network connection. This vulnerability appears to have been fixed after commit 3674815d1b0f7484454995e2737a352e0a6a93d8.","published":"2018-04-18T19:29:00.333Z","modified":"2026-07-08T12:28:39.184100Z","cvss":{"score":5.9,"severity":"MEDIUM","vector":"CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"tlslite-ng","fixedVersion":"0.7.4"}],"fix":{"url":"https://github.com/tomato42/tlslite-ng/pull/234","label":"tomato42/tlslite-ng#234"},"references":[{"type":"ADVISORY","url":"https://github.com/tomato42/tlslite-ng/pull/234"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T12:28:39.184100Z"}}