{"id":"CVE-2026-123613","kind":"vulnerability","aliases":["CVE-2026-123613"],"related":[],"title":"Rustls: TLS 1.3 handshake messages accepted unencrypted, letting on-path attackers inject","description":"Rustls from 0.23.13 before 0.23.45 accepts TLS 1.3 handshake messages at the wrong encryption level when they follow a key-changing message in the same record, because Deframer::aligned does not enforce RFC 8446 record-boundary alignment. A peer or on-path attacker can pack a plaintext EncryptedExtensions with the ServerHello, which rustls accepts unencrypted.","summary":"Rustls accepts TLS 1.3 handshake messages at the wrong encryption level when they follow a key-changing message in the same record, because record-boundary alignment is not enforced. A peer or on-path attacker can place a plaintext EncryptedExtensions message alongside the ServerHello, and rustls accepts it unencrypted.","severity":"medium","cvss":6.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["cargo","package","rust","rustls","tls"],"not_affected_if":["no-rustls-usage","version-outside-range"],"how_to_check":"- Find the `rustls` version in `Cargo.lock` or `cargo tree` output for each service.\n- Flag any version from `0.23.13` up to but not including `0.23.45`.\n- Check whether the TLS client or server path uses rustls at all, since only TLS 1.3 handshakes are described.","fix":"- `rustls` `0.23.45` (fixed version for the 0.23.x line, per the affected range 0.23.13 to before 0.23.45)","status":"open","published_at":"2026-11-08T02:16:56+00:00","first_seen_at":"2026-11-08T02:21:14+00:00","triaged_at":"2026-11-08T02:24:41+00:00","updated_at":"2026-11-08T02:24:41+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-11-08T02:24:41Z","model":"claude-haiku-5-5","output":{"fix":"- `rustls` `0.23.45` (fixed version for the 0.23.x line, per the affected range 0.23.13 to before 0.23.45)","reach":"network","title":"Rustls: TLS 1.3 handshake messages accepted unencrypted, letting on-path attackers inject","impact":"medium","summary":"Rustls accepts TLS 1.3 handshake messages at the wrong encryption level when they follow a key-changing message in the same record, because record-boundary alignment is not enforced. A peer or on-path attacker can place a plaintext EncryptedExtensions message alongside the ServerHello, and rustls accepts it unencrypted.","audience":"developers","category":"package","nicknames":[],"who_cares":["rustls","rust","tls","cargo"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"On-path attacker injects unencrypted handshake messages into TLS sessions","analyst_note":"","how_to_check":"- Find the `rustls` version in `Cargo.lock` or `cargo tree` output for each service.\n- Flag any version from `0.23.13` up to but not including `0.23.45`.\n- Check whether the TLS client or server path uses rustls at all, since only TLS 1.3 handshakes are described.","plain_action":"","needs_analyst":false,"not_affected_if":["version-outside-range","no-rustls-usage"],"who_is_affected":"Applications built on rustls 0.23.13 through 0.23.45 that accept TLS 1.3 connections. The attacker must be a peer or sit on the network path between client and server. Services that do not use rustls, or that run a version outside this range, are not affected.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.001129,"input_tokens":4328,"output_tokens":1393,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-123613':16A,19A '-2026':15A,18A '0.23.13':79C '0.23.45':81C '1.3':3A,28B,84C '8446':111C 'accept':6A,26B,74B,82C,133C 'align':52B,106C,115C 'alongsid':69B 'attack':12A,62B,122C 'boundari':51B,114C 'cargo':20B 'chang':42B,98C 'cve':14A,17A 'defram':105C 'encrypt':34B,90C 'encryptedextens':67B,127C 'enforc':55B,109C 'follow':38B,94C 'handshak':4A,29B,85C 'inject':13A 'key':41B,97C 'key-chang':40B,96C 'let':8A 'level':35B,91C 'messag':5A,30B,43B,68B,86C,99C 'on-path':9A,59B,119C 'pack':124C 'packag':21B 'path':11A,61B,121C 'peer':57B,117C 'place':64B 'plaintext':66B,126C 'record':47B,50B,103C,113C 'record-boundari':49B,112C 'rfc':110C 'rust':22B 'rustl':1A,23B,25B,73B,77C,132C 'serverhello':71B,130C 'tls':2A,24B,27B,83C 'unencrypt':7A,76B,134C 'wrong':33B,89C","nicknames":[],"mitigations":[],"who_affected":"Applications built on rustls 0.23.13 through 0.23.45 that accept TLS 1.3 connections. The attacker must be a peer or sit on the network path between client and server. Services that do not use rustls, or that run a version outside this range, are not affected.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["cargo","medium","package","rust","rustls","tls"],"campaign_type":null,"search_a":"'-123613':16A,19A '-2026':15A,18A '1.3':3A 'accept':6A 'attack':12A 'cve':14A,17A 'handshak':4A 'inject':13A 'let':8A 'messag':5A 'on-path':9A 'path':11A 'rustl':1A 'tls':2A 'unencrypt':7A","search_b":"'1.3':28B 'accept':26B,74B 'align':52B 'alongsid':69B 'attack':62B 'boundari':51B 'cargo':20B 'chang':42B 'encrypt':34B 'encryptedextens':67B 'enforc':55B 'follow':38B 'handshak':29B 'key':41B 'key-chang':40B 'level':35B 'messag':30B,43B,68B 'on-path':59B 'packag':21B 'path':61B 'peer':57B 'place':64B 'plaintext':66B 'record':47B,50B 'record-boundari':49B 'rust':22B 'rustl':23B,25B,73B 'serverhello':71B 'tls':24B,27B 'unencrypt':76B 'wrong':33B","search_c":"'0.23.13':79C '0.23.45':81C '1.3':84C '8446':111C 'accept':82C,133C 'align':106C,115C 'attack':122C 'boundari':114C 'chang':98C 'defram':105C 'encrypt':90C 'encryptedextens':127C 'enforc':109C 'follow':94C 'handshak':85C 'key':97C 'key-chang':96C 'level':91C 'messag':86C,99C 'on-path':119C 'pack':124C 'path':121C 'peer':117C 'plaintext':126C 'record':103C,113C 'record-boundari':112C 'rfc':110C 'rustl':77C,132C 'serverhello':130C 'tls':83C 'unencrypt':134C 'wrong':89C","first_public_at":"2026-09-14T15:12:15+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-123613","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123613","severity":null,"published_at":"2026-11-08T02:16:56+00:00","modified_at":"2026-11-08T02:16:56+00:00","first_seen_at":"2026-11-08T02:21:14+00:00","fetched_at":"2026-11-08T02:21:14+00:00","note":null}],"documents":[{"id":99377,"url":"https://github.com/rustls/rustls/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":99378,"url":"https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-09-14T15:12:15+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":99379,"url":"https://www.vulncheck.com/advisories/rustls-0.23.13-before-0.23.45-tls-1.3-handshake-encryption-level-bypass","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}