UBUNTU-CVE-2026-72084: Critical severity ubuntu/linux vulnerability
In the Linux kernel, the following vulnerability has been resolved: scsi: target: Bound PR-OUT TransportID parsing to the received buffer corescsi3decodespeciport() and corescsi3emulateregisterandmove() hand the raw PERSISTENT RESERVE OUT parameter buffer to targetparseprouttransportid() without telling it how many bytes are valid. For an iSCSI TransportID (FORMAT CODE 01b), iscsiparseprouttransportid() locates the ",i,0x" ISID separator with an unbounded strstr() (and on the error path prints the name with a further unbounded "%s"). An initiator can submit a TransportID whose iSCSI name contains neither a ",i,0x" substring nor a NUL terminator, filling the parameter list to its end, so the scan runs off the end of the buffer. When the parameter list spans more than one page the buffer is a multi-page vmap (transportkmapdatasg()), so the over-read walks into the trailing vmalloc guard page and oopses (KASAN: vmalloc-out-of-bounds in strstr). It is reachable by any fabric that delivers a PR OUT to a device exported through an iSCSI TPG, including a guest via vhost-scsi. Pass the number of received bytes down to the parser and validate the iSCSI TransportID's own self-described length (ADDITIONAL LENGTH + 4) once, up front: reject it if it is below the spc4r17 minimum or larger than the received buffer, then bound the separator search, the ISID walk and the name copy by that length. This is the length check the callers already perform after the parse (corescsi3decodespeciport() compares tidlen against tpdl, corescsi3emulateregisterandmove() validates it against datalength), moved ahead of the scan. Also drop the unbounded "%s" of the unterminated name. Add per-format explicit name-length checks before copying into istr, rather than silently truncating with mint: for FORMAT CODE 00b reject if the descriptor body (tidlen - 4 bytes) cannot fit in istr[TRANSPORTIQNLEN]; for FORMAT CODE 01b reject if the name portion (from &buf[4] up to the separator) cannot fit. Both checks make the bounds intent explicit at each format branch. While here, also reject a FORMAT CODE 01b TransportID whose ",i,0x" separator sits at the very end of the descriptor: that leaves an empty ISID and points the returned port nexus pointer at buf + tidlen, one past the descriptor, which the registration code (corescsi3locateprreg(), corescsi3allocregistration()) then dereferences as the ISID string -- the same over-read of the parameter buffer for a malformed descriptor.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1117.124~20.04.1 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70+fips1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-34.34 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-34.34.1 - Compensating control
Bound PR-OUT TransportID parsing to the received buffer: pass the number of received bytes from core_scsi3_decode_spec_i_port() and core_scsi3_emulate_register_and_move() to target_parse_pr_out_transport_id(); validate ADDITIONAL LENGTH + 4 once up front, rejecting values below the spc4r17 minimum or larger than the received buffer; bound the ",i,0x" separator search, ISID walk, and name copy by that length; reject FORMAT CODE 01b descriptors whose separator is at the end; perform explicit per-format name-length checks before copying into i_str (for FORMAT CODE 00b, ensure tid_len - 4 fits in i_str[TRANSPORT_IQN_LEN]; for FORMAT CODE 01b, ensure the name from &buf[4] through the separator fits); and replace the unbounded strstr() and "%s" name handling with bounded operations.
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Systems with a device exported through an iSCSI target portal group are exposed when a fabric can deliver PERSISTENT RESERVE OUT commands to that device. This also includes guests that can reach such an export through vhost-scsi.
What does an attacker need to send to trigger the failure?
An initiator must submit a PERSISTENT RESERVE OUT request containing an iSCSI TransportID whose name lacks the expected ",i,0x" separator and is not NUL-terminated before the end of the received parameter list. The failure is reachable without stated privileges or user interaction.
How might an affected system present during exploitation or testing?
A malformed request can cause the kernel to scan beyond the received buffer. If the parameter list spans more than one page, the over-read can reach a vmalloc guard page and produce an oops; KASAN may report a vmalloc-out-of-bounds access in strstr.