{"id":"CVE-2026-65626","kind":"vulnerability","aliases":["CVE-2026-65626"],"related":[],"title":"jose (Erlang): RSA1_5 decryption leaks padding validity, enabling Bleichenbacher attack","description":"The pure-Erlang RSAES-PKCS1-v1_5 decryption in the jose_jwa_pkcs1 module is a Bleichenbacher padding oracle. eme_pkcs1_decode/2 returns the recovered message when a decrypted block has valid PKCS#1 v1.5 padding (a leading 0x00 0x02, a padding string of at least eight non-zero bytes, and a 0x00 separator) and returns a distinct error result otherwise, and rsaes_pkcs1_decrypt/2 additionally returns {error, {badsize, _}} when the length check fails. The implementation applies no implicit-rejection countermeasure (RFC 8017 §7.2.2): it does not substitute a deterministic pseudo-random plaintext on a padding failure, so a one-bit padding-conformance signal leaks to the caller. Because the underlying modular exponentiation in dp/2 is a raw, non-blinded crypto:mod_pow/3, the padding check also stays distinguishable by timing even when an application normalizes every failure to a single error value.\n\nAn unauthenticated attacker who knows only the public RSA key and can submit ciphertexts to a decryption endpoint that unwraps RSA1_5 JWE keys (or otherwise calls decrypt_private/3 with rsa_pkcs1_padding) can use this oracle to recover the plaintext of intercepted ciphertexts, such as content-encryption keys and thus the protected message, or to forge signatures, through roughly 10^4 to 10^6 adaptive chosen-ciphertext queries.\n\nThis issue affects jose: from 1.3.0 before 1.11.13.","summary":"The Erlang jose library's pure-Erlang RSAES-PKCS1-v1_5 decryption acts as a Bleichenbacher padding oracle, with no implicit rejection and non-blinded modular exponentiation. An attacker who can submit ciphertexts to an endpoint that unwraps RSA1_5 keys can recover plaintexts such as content-encryption keys in roughly 10^4 to 10^6 queries.","severity":"medium","cvss":5.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["elixir","erlang","jose","jwe","package"],"not_affected_if":["jose-1.11.13-or-later","no-rsa1_5-decryption","oaep-only"],"how_to_check":"- Check the jose version in `rebar.lock` or `mix.lock` (Erlang/Elixir projects), e.g. `grep jose rebar.lock mix.lock`\n- Search application code for RSA1_5 JWE decryption or `decrypt_private/3` with `rsa_pkcs1_padding`","fix":"- Upgrade jose to `1.11.13` or later\n- Where possible, stop accepting RSA1_5 key wrapping and move to RSA-OAEP or ECDH-ES","status":"open","published_at":"2026-10-26T20:17:58+00:00","first_seen_at":"2026-10-26T20:50:17+00:00","triaged_at":"2026-10-26T20:51:50+00:00","updated_at":"2026-10-26T20:51:50+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-26T20:51:50Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade jose to `1.11.13` or later\n- Where possible, stop accepting RSA1_5 key wrapping and move to RSA-OAEP or ECDH-ES","reach":"internet","title":"jose (Erlang): RSA1_5 decryption leaks padding validity, enabling Bleichenbacher attack","impact":"high","summary":"The Erlang jose library's pure-Erlang RSAES-PKCS1-v1_5 decryption acts as a Bleichenbacher padding oracle, with no implicit rejection and non-blinded modular exponentiation. An attacker who can submit ciphertexts to an endpoint that unwraps RSA1_5 keys can recover plaintexts such as content-encryption keys in roughly 10^4 to 10^6 queries.","category":"package","nicknames":[],"who_cares":["erlang","elixir","jose","jwe"],"confidence":0.7,"needs_auth":"no","worst_case":"Attacker recovers encrypted content keys and forges signatures remotely","analyst_note":"Confirm the exact set of affected decrypt paths and whether the NVD entry lists fixed-version details beyond 1.11.13; source is https://nvd.nist.gov/vuln/detail/CVE-2026-65626.","how_to_check":"- Check the jose version in `rebar.lock` or `mix.lock` (Erlang/Elixir projects), e.g. `grep jose rebar.lock mix.lock`\n- Search application code for RSA1_5 JWE decryption or `decrypt_private/3` with `rsa_pkcs1_padding`","needs_analyst":true,"not_affected_if":["no-rsa1_5-decryption","oaep-only","jose-1.11.13-or-later"],"who_is_affected":"Applications that use the jose Erlang library from 1.3.0 before 1.11.13 and expose a decryption path that accepts RSA1_5 JWE keys or calls decrypt_private/3 with rsa_pkcs1_padding on attacker-supplied ciphertexts. Systems that only verify signatures or use OAEP padding are not exposed through this oracle.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"medium"},"cost_usd":0.000766,"input_tokens":3790,"output_tokens":773,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-65626':14A,17A '0x00':124C,139C '0x02':125C '1':119C '1.11.13':313C '1.3.0':311C '10':78B,81B,296C,299C '4':79B,297C '5':4A,35B,65B,92C,256C '6':82B,300C '7.2.2':171C '8017':170C 'act':37B 'adapt':301C 'addit':152C 'affect':308C 'also':218C 'appli':163C 'applic':226C 'attack':11A,54B,237C 'badsiz':155C 'bit':190C 'bleichenbach':10A,40B,102C 'blind':50B,211C 'block':115C 'byte':136C 'call':261C 'caller':198C 'check':159C,217C 'chosen':303C 'chosen-ciphertext':302C 'ciphertext':58B,248C,278C,304C 'conform':193C 'content':73B,282C 'content-encrypt':72B,281C 'countermeasur':168C 'crypto':212C 'cve':12A,15A 'decode/2':107C 'decrypt':5A,36B,93C,114C,251C,262C 'decrypt/2':151C 'determinist':177C 'distinct':144C 'distinguish':220C 'dp/2':205C 'eight':132C 'elixir':18B 'eme':105C 'enabl':9A 'encrypt':74B,283C 'endpoint':61B,252C 'erlang':2A,19B,24B,30B,87C 'error':145C,154C,233C 'even':223C 'everi':228C 'exponenti':52B,203C 'fail':160C 'failur':185C,229C 'forg':292C 'implement':162C 'implicit':45B,166C 'implicit-reject':165C 'intercept':277C 'issu':307C 'jose':1A,20B,25B,96C,309C 'jwa':97C 'jwe':21B,257C 'key':66B,75B,244C,258C,284C 'know':239C 'lead':123C 'leak':6A,195C 'least':131C 'length':158C 'librari':26B 'messag':111C,289C 'mod':213C 'modul':99C 'modular':51B,202C 'non':49B,134C,210C 'non-blind':48B,209C 'non-zero':133C 'normal':227C 'one':189C 'one-bit':188C 'oracl':42B,104C,271C 'otherwis':147C,260C 'packag':22B 'pad':7A,41B,103C,121C,127C,184C,192C,216C,267C 'padding-conform':191C 'pkcs':118C 'pkcs1':33B,90C,98C,106C,150C,266C 'plaintext':69B,181C,275C 'pow/3':214C 'private/3':263C 'protect':288C 'pseudo':179C 'pseudo-random':178C 'public':242C 'pure':29B,86C 'pure-erlang':28B,85C 'queri':83B,305C 'random':180C 'raw':208C 'recov':68B,110C,273C 'reject':46B,167C 'result':146C 'return':108C,142C,153C 'rfc':169C 'rough':77B,295C 'rsa':243C,265C 'rsa1':3A,64B,255C 'rsae':32B,89C,149C 'rsaes-pkcs1-v1':31B,88C 'separ':140C 'signal':194C 'signatur':293C 'singl':232C 'stay':219C 'string':128C 'submit':57B,247C 'substitut':175C 'thus':286C 'time':222C 'unauthent':236C 'under':201C 'unwrap':63B,254C 'use':269C 'v1':34B,91C 'v1.5':120C 'valid':8A,117C 'valu':234C 'zero':135C","nicknames":[],"mitigations":[],"who_affected":"Applications that use the jose Erlang library from 1.3.0 before 1.11.13 and expose a decryption path that accepts RSA1_5 JWE keys or calls decrypt_private/3 with rsa_pkcs1_padding on attacker-supplied ciphertexts. Systems that only verify signatures or use OAEP padding are not exposed through this oracle.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-26T20:17:58+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/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":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-65626","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-65626","severity":null,"published_at":"2026-10-26T20:17:58+00:00","modified_at":"2026-10-26T20:17:58+00:00","first_seen_at":"2026-10-26T20:50:17+00:00","fetched_at":"2026-10-26T20:50:17+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}