{"id":"DEBIAN-CVE-2026-63888","details":"In the Linux kernel, the following vulnerability has been resolved:  scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()  Two latent bugs in the Text-phase handler, both present since the original LIO integration in commit e48354ce078c (\"iscsi-target: Add iSCSI fabric support for target v4.1\"):  1) DataDigest CRC buffer overread (4 bytes past text_in).     text_in is kzalloc()'d at ALIGN(payload_length, 4).  rx_size is then    incremented by ISCSI_CRC_LEN to make room for the received DataDigest    in the iovec, but the same (now-bumped) rx_size is passed as the    buffer length to iscsit_crc_buf():         if (conn-\u003econn_ops-\u003eDataDigest) {                ...                rx_size += ISCSI_CRC_LEN;        }        ...        if (conn-\u003econn_ops-\u003eDataDigest) {                data_crc = iscsit_crc_buf(text_in, rx_size, 0, NULL);     iscsit_crc_buf() walks rx_size bytes of text_in with crc32c(), so    when DataDigest is negotiated it reads 4 bytes past the end of the    text_in allocation.  KASAN reproduces this directly on the unpatched    mainline tree as slab-out-of-bounds in crc32c() called from the Text    PDU path.  The OOB bytes feed crc32c() and are then compared against    the initiator-supplied checksum, so the value does not flow back to    the attacker, but the kernel does read past the buffer on every Text    PDU with DataDigest=CRC32C.     Fix by passing the actual padded payload length    (ALIGN(payload_length, 4)) that was used for the kzalloc().  2) Stale cmd-\u003etext_in_ptr re-free (double-free) on ERL\u003e0 bad DataDigest    drop.     On DataDigest mismatch with ErrorRecoveryLevel \u003e 0 the handler    silently drops the PDU and lets the initiator plug the CmdSN gap:                 kfree(text_in);                return 0;     cmd-\u003etext_in_ptr still points at the freed buffer.  The next Text    Request on the same ITT re-enters iscsit_setup_text_cmd(), which    unconditionally does         kfree(cmd-\u003etext_in_ptr);        cmd-\u003etext_in_ptr = NULL;     freeing the same pointer a second time.  Session teardown via    iscsit_release_cmd() has the same shape and hits the same double-free    if the connection is dropped before a second Text Request arrives.     On an unmodified mainline tree the bug-1 CRC overread fires first on    the initial valid Text Request and perturbs the subsequent state, so    #4 was isolated by building a kernel with only the bug-1 hunk of this    patch applied plus temporary printk() observability around the three    relevant kfree() sites.  The observability prints are not part of    this patch.  On that build, a three-PDU Text Request sequence after    login produces two back-to-back splats:         BUG: KASAN: double-free in iscsit_setup_text_cmd+0x??        BUG: KASAN: double-free in iscsit_release_cmd+0x??     showing the same pointer freed in the ERL\u003e0 drop path and again in    iscsit_setup_text_cmd() (next Text Request on the same ITT) and once    more in iscsit_release_cmd() (session teardown).  On distro kernels    with CONFIG_SLAB_FREELIST_HARDENED=y (default) the double-free    becomes a remote kernel BUG(); on non-hardened kernels it corrupts    the slab freelist.     Fix by clearing cmd-\u003etext_in_ptr after the kfree() in the ERL\u003e0 drop    path.  With both hunks applied #4 is directly observable on the stock    tree without observability printks; fixing bug-1 alone would mask #4    less, not more, so the hunks are submitted together.  Both fixes are one-liners.  The Text PDU state machine is unchanged and the wire protocol is unaffected.","modified":"2026-09-29T13:04:14.515205172Z","published":"2026-07-19T16:17:05.997Z","upstream":["CVE-2026-63888"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-63888"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.176-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63888.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.94-1"}]}],"versions":["6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1~bpo12+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63888.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.0.12-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.111-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.10-1","6.19.10-1~bpo13+1","6.19.11-1","6.19.11-1~bpo13+1","6.19.12-1","6.19.13-1","6.19.13-1~bpo13+1","6.19.14-1","6.19.14-1~bpo13+1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1","7.0-1~exp1","7.0.1-1~exp1","7.0.10-1","7.0.10-1~bpo13+1","7.0.3-1","7.0.4-1","7.0.4-1~bpo13+1","7.0.7-1","7.0.7-1~bpo13+1","7.0.9-1","7.0.9-1~bpo13+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63888.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}