CVE-2026-63886

CVE CVE-2026-63886EUVD EUVD-2026-45771Veröffentlicht 2026-07-19T14:54:59.000ZZuletzt geändert 2026-08-05T12:36:55.000ZCVSS 9.8

Was das Advisory beschreibt

In the Linux kernel, the following vulnerability has been resolved: scsi: target: iscsi: Validate CHAP_R length before base64 decode chap_server_compute_hash() allocates client_digest as kzalloc(chap->digest_size) and then, for BASE64-encoded responses, passes chap_r directly to chap_base64_decode() without checking whether the input length could produce more than digest_size bytes of output. chap_base64_decode() writes to the destination unconditionally as long as there is input to consume. With MAX_RESPONSE_LENGTH set to 128 and the "0b" prefix stripped by extract_param(), up to 127 base64 characters can reach the decoder. 127 characters decode to 95 bytes. For SHA-256 (digest_size=32) this overflows client_digest by 63 bytes; for MD5 (digest_size=16) the overflow is 79 bytes. The length check at line 344 fires after the write has already happened. The HEX branch in the same switch statement already validates the length up front. Apply the same approach to the BASE64 branch: strip trailing base64 padding characters, then reject any input whose data length exceeds DIV_ROUND_UP(digest_size * 4, 3) before calling the decoder. Stripping trailing '=' before the comparison handles both padded and unpadded encodings. chap_base64_decode() already returns early on '=', so the full original string is still passed to the decoder unchanged. The mutual CHAP path decodes CHAP_C into initiatorchg_binhex, which is kzalloc(CHAP_CHALLENGE_STR_LEN). extract_param() caps initiatorchg at CHAP_CHALLENGE_STR_LEN characters, so at most CHAP_CHALLENGE_STR_LEN-1 base64 characters reach the decoder. The maximum decoded size, DIV_ROUND_UP((CHAP_CHALLENGE_STR_LEN-1) * 3, 4), is less than CHAP_CHALLENGE_STR_LEN, so no overflow is possible there. A comment is added at the call site to document this.

Quelle: EUVD (ENISA), im Wortlaut der Meldung.

Produkte, die das Advisory nennt

Diese Angaben stammen aus der Meldung selbst, nicht aus einer Prüfung durch uns.

• Linux — Linux 1e5733883421495908f3b90d9d807663038b4136 <c04e85799356120209b351a148ac2db888d5ffd9; patch: 6.6.143; 1e5733883421495908f3b90d9d807663038b4136 <edd06675a02376ea8347dba7c29ad982ba5b36ee; 1e5733883421495908f3b90d9d807663038b4136 <4a3a19c98a8207ad08bec554703d90f2c34a8cc6; patch: 0; 1e5733883421495908f3b90d9d807663038b4136 <85db7391310b1304d2dc8ae3b0b12105a9567147; patch: 7.1; patch: 6.12.93; 1e5733883421495908f3b90d9d807663038b4136 <82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6; patch: 6.18.35; 6.0; patch: 7.0.12; patch: 6.1.176; 1e5733883421495908f3b90d9d807663038b4136 <bf154c657828ed05399bca5d98cf1611bb048b12

Die genannten Versionen sind die Angabe der Meldung. Patchlage vergleicht keine Versionsnummern und leitet aus ihnen keine Aussage ab — welche Version installiert ist, muss ein Mensch nachsehen.

Im Produktkatalog geführt

Für diese Produkte kann ein Bestand in Patchlage erfasst werden. Ein Advisory dazu erscheint am Morgen danach im Lagebericht.

• Linux — Linux

Patchlage meldet Treffer und Verdachtsfälle. Zu allem anderen sagt dieses System nichts — weder diese Seite noch der Lagebericht behauptet je, dass ein Bestand sicher ist.