UBUNTU-CVE-2026-63887
In the Linux kernel, the following vulnerability has been resolved: scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf iscsi_encode_text_output() concatenates "key=value\0" records into login->rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer allocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check the remaining buffer capacity: *length += sprintf(output_buf, "%s=%s", er->key, er->value); *length += 1; output_buf = textbuf + *length; The 8192-byte ceiling at iscsi_target_check_login_request() bounds the *input* Login PDU payload, but a single PDU can carry up to 2048 minimal four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte "a=NotUnderstood\0" output record via iscsi_add_notunderstood_response(). 2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB heap overrun in the kmalloc-8k slab. The fix introduces a static iscsi_encode_text_record() helper that uses snprintf() with a per-call bounds check against the remaining buffer, and threads a u32 textbuf_size parameter through iscsi_encode_text_output(). Both call sites in iscsi_target_handle_csg_zero() (PHASE_SECURITY) and iscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass MAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls iscsi_release_extra_responses() to drop queued records, and returns -1; both caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR / ISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning, so the initiator sees an explicit failed-login response rather than a silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL caller did that; the PHASE_SECURITY caller is converted to the same shape.)
02 / AFFECTED SOFTWARE
Affected packages
68 explicit affected versions
120 explicit affected versions
13 explicit affected versions
8 explicit affected versions
11 explicit affected versions
4 explicit affected versions
53 explicit affected versions
167 explicit affected versions
86 explicit affected versions
116 explicit affected versions
89 explicit affected versions
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
19 explicit affected versions
10 explicit affected versions
6 explicit affected versions
100 explicit affected versions
61 explicit affected versions
24 explicit affected versions
2 explicit affected versions
85 explicit affected versions
84 explicit affected versions
91 explicit affected versions
76 explicit affected versions
10 explicit affected versions
39 explicit affected versions
26 explicit affected versions
90 explicit affected versions
191 explicit affected versions
7 explicit affected versions
84 explicit affected versions
42 explicit affected versions
13 explicit affected versions
85 explicit affected versions
46 explicit affected versions
35 explicit affected versions
1 explicit affected versions
51 explicit affected versions
50 explicit affected versions
18 explicit affected versions
48 explicit affected versions
42 explicit affected versions
118 explicit affected versions
1 explicit affected versions
64 explicit affected versions
13 explicit affected versions
4 explicit affected versions
121 explicit affected versions
23 explicit affected versions
55 explicit affected versions
124 explicit affected versions
1 explicit affected versions
1 explicit affected versions
21 explicit affected versions
9 explicit affected versions
16 explicit affected versions
10 explicit affected versions
76 explicit affected versions
7 explicit affected versions
51 explicit affected versions
8 explicit affected versions
7 explicit affected versions
12 explicit affected versions
11 explicit affected versions
111 explicit affected versions
7 explicit affected versions
12 explicit affected versions
14 explicit affected versions
1 explicit affected versions
7 explicit affected versions
19 explicit affected versions
104 explicit affected versions
12 explicit affected versions
10 explicit affected versions
1 explicit affected versions
105 explicit affected versions
12 explicit affected versions
44 explicit affected versions
9 explicit affected versions
9 explicit affected versions
120 explicit affected versions
45 explicit affected versions
16 explicit affected versions
6 explicit affected versions
29 explicit affected versions
37 explicit affected versions
10 explicit affected versions
37 explicit affected versions
10 explicit affected versions
11 explicit affected versions
13 explicit affected versions
42 explicit affected versions
3 explicit affected versions
10 explicit affected versions
11 explicit affected versions
26 explicit affected versions
12 explicit affected versions
13 explicit affected versions
144 explicit affected versions
37 explicit affected versions
96 explicit affected versions
1 explicit affected versions
29 explicit affected versions
111 explicit affected versions
13 explicit affected versions
12 explicit affected versions
43 explicit affected versions
43 explicit affected versions
8 explicit affected versions
1 explicit affected versions
92 explicit affected versions
100 explicit affected versions
10 explicit affected versions
55 explicit affected versions
33 explicit affected versions
23 explicit affected versions
60 explicit affected versions
23 explicit affected versions
188 explicit affected versions
22 explicit affected versions
11 explicit affected versions
5 explicit affected versions
12 explicit affected versions
11 explicit affected versions
7 explicit affected versions
12 explicit affected versions
10 explicit affected versions
138 explicit affected versions
17 explicit affected versions
2 explicit affected versions
5 explicit affected versions
77 explicit affected versions
132 explicit affected versions
93 explicit affected versions
165 explicit affected versions
154 explicit affected versions
10 explicit affected versions
26 explicit affected versions
42 explicit affected versions
1 explicit affected versions
69 explicit affected versions
37 explicit affected versions
48 explicit affected versions
11 explicit affected versions
10 explicit affected versions
13 explicit affected versions
48 explicit affected versions
139 explicit affected versions
78 explicit affected versions
16 explicit affected versions
91 explicit affected versions
53 explicit affected versions
10 explicit affected versions
116 explicit affected versions
3 explicit affected versions
132 explicit affected versions
93 explicit affected versions
1 explicit affected versions
7 explicit affected versions
2 explicit affected versions
51 explicit affected versions
92 explicit affected versions
18 explicit affected versions
43 explicit affected versions
12 explicit affected versions
71 explicit affected versions
80 explicit affected versions
7 explicit affected versions
27 explicit affected versions
3 explicit affected versions
66 explicit affected versions
121 explicit affected versions
1 explicit affected versions
8 explicit affected versions
1 explicit affected versions
98 explicit affected versions
45 explicit affected versions
8 explicit affected versions
55 explicit affected versions
3 explicit affected versions
5 explicit affected versions
8 explicit affected versions
6 explicit affected versions
1 explicit affected versions
10 explicit affected versions
7 explicit affected versions
49 explicit affected versions
110 explicit affected versions
13 explicit affected versions
72 explicit affected versions
7 explicit affected versions
140 explicit affected versions
94 explicit affected versions
10 explicit affected versions
12 explicit affected versions
9 explicit affected versions
9 explicit affected versions
39 explicit affected versions
108 explicit affected versions
80 explicit affected versions
56 explicit affected versions
44 explicit affected versions
11 explicit affected versions
16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
45 explicit affected versions
37 explicit affected versions
53 explicit affected versions
14 explicit affected versions
38 explicit affected versions
42 explicit affected versions
21 explicit affected versions
92 explicit affected versions
8 explicit affected versions
7 explicit affected versions
97 explicit affected versions
121 explicit affected versions
4 explicit affected versions
81 explicit affected versions
10 explicit affected versions
1 explicit affected versions
1 explicit affected versions
1 explicit affected versions
91 explicit affected versions
80 explicit affected versions
79 explicit affected versions
7 explicit affected versions
13 explicit affected versions
43 explicit affected versions
77 explicit affected versions
16 explicit affected versions
119 explicit affected versions
5 explicit affected versions
10 explicit affected versions
8 explicit affected versions
48 explicit affected versions
88 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
11 explicit affected versions
1 explicit affected versions
69 explicit affected versions
123 explicit affected versions
22 explicit affected versions
6 explicit affected versions
41 explicit affected versions
80 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf iscsi_encode_text_output() concatenates "key=value\0" records into login->rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer allocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check the remaining buffer capacity: *length += sprintf(output_buf, "%s=%s", er->key, er->value); *length += 1; output_buf = textbuf + *length; The 8192-byte ceiling at iscsi_target_check_login_request() bounds the *input* Login PDU payload, but a single PDU can carry up to 2048 minimal four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte "a=NotUnderstood\0" output record via iscsi_add_notunderstood_response(). 2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB heap overrun in the kmalloc-8k slab. The fix introduces a static iscsi_encode_text_record() helper that uses snprintf() with a per-call bounds check against the remaining buffer, and threads a u32 textbuf_size parameter through iscsi_encode_text_output(). Both call sites in iscsi_target_handle_csg_zero() (PHASE_SECURITY) and iscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass MAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls iscsi_release_extra_responses() to drop queued records, and returns -1; both caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR / ISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning, so the initiator sees an explicit failed-login response rather than a silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL caller did that; the PHASE_SECURITY caller is converted to the same shape.)
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/bf33e01f88388c43e285492a63e539df6ffed64c
- https://ubuntu.com/security/CVE-2026-63887
- https://ubuntu.com/security/notices/USN-8593-1
- https://ubuntu.com/security/notices/USN-8603-1
- https://ubuntu.com/security/notices/USN-8618-1
- https://www.cve.org/CVERecord?id=CVE-2026-63887