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.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it