{"id":"CVE-2023-23931","aliases":["GHSA-w7pp-m8wf-vj6r","PYSEC-2023-11"],"title":"Cipher.update_into can corrupt memory if passed an immutable python object as the outbuf","summary":"Cipher.update_into can corrupt memory if passed an immutable python object as the outbuf","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L","vendor":"cryptography","product":"cryptography","ecosystem":"pip","affected":["cryptography >= 1.8, < 39.0.1"],"patched":["cryptography 39.0.1"],"published":"2023-02-07","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:49:52.124485319Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-w7pp-m8wf-vj6r","references":[{"url":"https://github.com/pyca/cryptography/security/advisories/GHSA-w7pp-m8wf-vj6r"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-23931"},{"url":"https://github.com/pyca/cryptography/pull/8230"},{"url":"https://github.com/pyca/cryptography/commit/d6951dca25de45abd52da51b608055371fbcde4e"},{"url":"https://github.com/pyca/cryptography"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2023-11.yaml"},{"url":"https://lists.debian.org/debian-lts-announce/2024/10/msg00012.html"},{"url":"https://security.netapp.com/advisory/ntap-20230324-0007"}],"tags":["osv","pip"],"epss":0.01301,"epssPercentile":0.68737,"ingestedAt":"2026-09-12T03:13:01.733Z","slug":"CVE-2023-23931","body":"## Overview\n\nPreviously, `Cipher.update_into` would accept Python objects which implement the buffer protocol, but provide only immutable buffers:\n\n```pycon\n>>> outbuf = b\"\\x00\" * 32\n>>> c = ciphers.Cipher(AES(b\"\\x00\" * 32), modes.ECB()).encryptor()\n>>> c.update_into(b\"\\x00\" * 16, outbuf)\n16\n>>> outbuf\nb'\\xdc\\x95\\xc0x\\xa2@\\x89\\x89\\xadH\\xa2\\x14\\x92\\x84 \\x87\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00'\n```\n\nThis would allow immutable objects (such as `bytes`) to be mutated, thus violating fundamental rules of Python. This is a soundness bug -- it allows programmers to misuse an API, it cannot be exploited by attacker controlled data alone.\n\nThis now correctly raises an exception.\n\nThis issue has been present since `update_into` was originally introduced in cryptography 1.8.\n\n## Affected packages\n\n- `cryptography >= 1.8, < 39.0.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `cryptography 39.0.1`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.3,"exploitation":0,"ransomware":0},"changes":[]}