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CVE-2026-63886 is a heap-based buffer overflow in the Linux kernel's SCSI iSCSI target CHAP authentication implementation. chap_server_compute_hash() allocates client_digest according to the selected digest size but passes Base64-encoded CHAP_R responses to chap_base64_decode() without first checking whether the decoded output fits. Up to 127 Base64 characters can reach the decoder and produce 95 bytes, overflowing a 32-byte SHA-256 digest buffer by 63 bytes or a 16-byte MD5 digest buffer by 79 bytes. The existing length check occurs after the out-of-bounds write. The hexadecimal response branch and mutual CHAP challenge-decoding path are not affected by this overflow.
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A vulnerability covered by the Miracle Linux kernel security update AXSA-2026-1991. No flaw-specific technical description is provided.
Insufficient validation of CHAP_R length before Base64 decoding in the Linux kernel iSCSI target implementation.
A heap buffer overflow in the Linux kernel's iSCSI target CHAP authentication handling. Base64-encoded CHAP_R responses are decoded into a digest-sized allocation before their length is validated. An input of 127 base64 characters can produce 95 bytes, overflowing a SHA-256 digest buffer by 63 bytes or an MD5 buffer by 79 bytes. The fix validates the input length before decoding, accounting for trailing padding. The reference assigns CVSS v3 9.8, although vendor severity is LOW, and reports no known exploits.
A heap buffer overflow in the Linux kernel's iSCSI target CHAP authentication handling. An insufficiently validated Base64-encoded CHAP_R response can decode to 95 bytes, overflowing a 32-byte SHA-256 digest buffer by 63 bytes or a 16-byte MD5 buffer by 79 bytes. The existing length check occurs after the write. The plugin assigns a CVSS v3 base score of 9.8, although vendor severity is LOW. The fix validates the input length before decoding, accounting for trailing Base64 padding.
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