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Review reviewCritical

CVE-2026-63886

Linux

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 base6...

CVSS
9.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.20
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 9.8

Vulnerability overview

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 base6...

Affected product and versions

Product
Linux
Affected versions
>= 1e5733883421495908f3b90d9d807663038b4136 < 82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6, >= 1e5733883421495908f3b90d9d807663038b4136 < edd06675a02376ea8347dba7c29ad982ba5b36ee, >= 1e5733883421495908f3b90d9d807663038b4136 < bf154c657828ed05399bca5d98cf1611bb048b12, >= 1e5733883421495908f3b90d9d807663038b4136 < 4a3a19c98a8207ad08bec554703d90f2c34a8cc6, >= 1e5733883421495908f3b90d9d807663038b4136 < c04e85799356120209b351a148ac2db888d5ffd9, >= 1e5733883421495908f3b90d9d807663038b4136 < 85db7391310b1304d2dc8ae3b0b12105a9567147, >= 6.0
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
Not available
CVE-2026-63886 — Linux | SECUFOCUS NOW