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CVE-2026-63887

scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

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.)

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in cb84e974fb172bc71386289f37b78ea679410b39; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in b19382dfc6e7dee6d3859ba44b6ca29e97a51627; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in efe633e600a0ac68357206fede21b1ac8178f3b8; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in 4e9f0c4a645c995bc75c06c7b3644254ffb4c76b; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in 30bf335e8fe170322080ee001f05ca29c50680b3; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in 594a40360012ce5f94c715d5e3b20fa3af7d525a; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in 26e4a304b7e6f1338c675d527608d32549c091db; From e48354ce078c079996f89d715dfa44814b4eba01 · fixed in bf33e01f88388c43e285492a63e539df6ffed64c

  • Linux Linux

    3.1

  • KernelLinux

    From 3.1.0 · fixed in 5.10.259; From 5.11.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.143; From 6.7.0 · fixed in 6.12.93; From 6.13.0 · fixed in 6.18.35; From 6.19.0 · fixed in 7.0.12

References 8

git.kernel.org