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CVE-2026-74557
scsi: libiscsi: Fix stale-data leak into the SCSI sense buffer
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/scsi. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74557 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
iscsi_scsi_cmd_rsp() copies the sense data of a SCSI Response from the target-supplied data segment. The segment carries a 2-byte sense length followed by the sense bytes, so it must hold 2 + senselen bytes, but the bounds check only requires datalen >= senselen: senselen = get_unaligned_be16(data); if (datalen < senselen) goto invalid_datalen; memcpy(sc->sense_buffer, data + 2, min_t(uint16_t, senselen, SCSI_SENSE_BUFFERSIZE)); A target that returns a SCSI Response whose datalen equals senselen (with senselen <= SCSI_SENSE_BUFFERSIZE) makes the memcpy() from data + 2 read up to two bytes past the received data. Those bytes are stale conn->data contents and end up in the command's sense buffer, which is returned to userspace. Account for the 2-byte sense length prefix in the check.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/scsi/libiscsi.c
- What this is
- ISCSIMAINTAINERS section matched on drivers/scsi/*iscsi* · open-iscsi@googlegroups.com · Maintained
- Kernel module
- libiscsi
Check it on the machine
grep -wE 'CONFIG_BE2ISCSI|CONFIG_INFINIBAND_ISER|CONFIG_ISCSI_TCP|CONFIG_QEDI|CONFIG_SCSI_BNX2_ISCSI|CONFIG_SCSI_CXGB3_ISCSI|CONFIG_SCSI_CXGB4_ISCSI|CONFIG_SCSI_QLA_ISCSI' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w libiscsiPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_BE2ISCSI, CONFIG_INFINIBAND_ISER, CONFIG_ISCSI_TCP, CONFIG_QEDI, CONFIG_SCSI_BNX2_ISCSI, CONFIG_SCSI_CXGB3_ISCSI, CONFIG_SCSI_CXGB4_ISCSI, CONFIG_SCSI_QLA_ISCSI
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:Nsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.33%, higher than 24.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/scsi
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.18 | 5.10.265 | 812f1ae95b22 |
| 2.6.18 | 5.15.216 | fef6167e8149 |
| 2.6.18 | 6.1.183 | baa045726731 |
| 2.6.18 | 6.6.151 | 7567f06abdef |
| 2.6.18 | 6.12.103 | 60499924faf4 |
| 2.6.18 | 6.18.44 | 3ef209ca0b4b |
| 2.6.18 | 7.1.8 | 1f07a897d43c |
| 2.6.18 | 7.2 | 98b87885de4b |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- A remote malicious or compromised iSCSI target can trigger the bug by sending a crafted SCSI Command Response over the standard iSCSI/TCP session to a Linux kernel initiator, with no local access required on the victim host.
- AC:LAttack complexity, low
- The attacker fully controls the response PDU fields (datalen, sense length, CHECK_CONDITION status) and can reliably set datalen equal to senselen so the flawed bounds check passes and stale conn->data bytes are copied into the sense buffer.
- PR:NPrivileges required, none
- Exploitation requires only the ability to act as the iSCSI target on the network; the attacker needs no local account, capabilities, or privileges on the victim system initiating the connection.
- UI:NUser interaction, none
- Once an iSCSI session exists, the leak is triggered automatically on SCSI command responses with no further victim action; the attacker does not rely on a user opening a file, clicking a link, or performing any interactive step at exploit time.
- S:UScope, unchanged
- The flaw discloses kernel memory contents into a SCSI sense buffer returned within the same host security domain; it does not cross VM, hypervisor, or IOMMU boundaries and is a standard kernel-to-userspace information leak.
- C:HConfidentiality impact, high
- The out-of-bounds memcpy reads up to two bytes per response from stale conn->data kernel heap memory into sc->sense_buffer, which is copied to userspace via SCSI completion, ioctl, and BSG paths, enabling repeated kernel information disclosure.
- I:NIntegrity impact, none
- The vulnerability is a read-only out-of-bounds memcpy from the receive buffer into the sense buffer; it does not corrupt kernel structures, overwrite memory, or provide a write or code-execution primitive.
- A:NAvailability impact, none
- The bug causes no kernel panic, oops, or hang; invalid responses are handled gracefully and exploitation only leaks data into the sense buffer without disrupting system availability.