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This CVE is currently being enriched by team members, this process results in the association of reference link tags, CVSS, CWE, and CPE applicability statement data.
Description
In the Linux kernel, the following vulnerability has been resolved:
dm-verity-fec: fix reading parity bytes split across blocks (take 3)
fec_decode_bufs() assumes that the parity bytes of the first RS codeword
it decodes are never split across parity blocks.
This assumption is false. Consider v->fec->block_size == 4096 &&
v->fec->roots == 17 && fio->nbufs == 1, for example. In that case, each
call to fec_decode_bufs() consumes v->fec->roots * (fio->nbufs <<
DM_VERITY_FEC_BUF_RS_BITS) = 272 parity bytes.
Considering that the parity data for each message block starts on a
block boundary, the byte alignment in the parity data will iterate
through 272*i mod 4096 until the 3 parity blocks have been consumed. On
the 16th call (i=15), the alignment will be 4080 bytes into the first
block. Only 16 bytes remain in that block, but 17 parity bytes will be
needed. The code reads out-of-bounds from the parity block buffer.
Fortunately this doesn't normally happen, since it can occur only for
certain non-default values of fec_roots *and* when the maximum number of
buffers couldn't be allocated due to low memory. For example with
block_size=4096 only the following cases are affected:
fec_roots=17: nbufs in [1, 3, 5, 15]
fec_roots=19: nbufs in [1, 229]
fec_roots=21: nbufs in [1, 3, 5, 13, 15, 39, 65, 195]
fec_roots=23: nbufs in [1, 89]
Regardless, fix it by refactoring how the parity blocks are read.
Metrics
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OR
*cpe:2.3:o:linux:linux_kernel:6.13:rc7:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:6.13:-:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.1.125 up to (excluding) 6.2
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.12.10 up to (excluding) 6.13
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13.1 up to (excluding) 7.0.7
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.6.72 up to (excluding) 6.7
New CVE Received from kernel.org5/28/2026 6:16:28 AM
Action
Type
Old Value
New Value
Added
Description
In the Linux kernel, the following vulnerability has been resolved:
dm-verity-fec: fix reading parity bytes split across blocks (take 3)
fec_decode_bufs() assumes that the parity bytes of the first RS codeword
it decodes are never split across parity blocks.
This assumption is false. Consider v->fec->block_size == 4096 &&
v->fec->roots == 17 && fio->nbufs == 1, for example. In that case, each
call to fec_decode_bufs() consumes v->fec->roots * (fio->nbufs <<
DM_VERITY_FEC_BUF_RS_BITS) = 272 parity bytes.
Considering that the parity data for each message block starts on a
block boundary, the byte alignment in the parity data will iterate
through 272*i mod 4096 until the 3 parity blocks have been consumed. On
the 16th call (i=15), the alignment will be 4080 bytes into the first
block. Only 16 bytes remain in that block, but 17 parity bytes will be
needed. The code reads out-of-bounds from the parity block buffer.
Fortunately this doesn't normally happen, since it can occur only for
certain non-default values of fec_roots *and* when the maximum number of
buffers couldn't be allocated due to low memory. For example with
block_size=4096 only the following cases are affected:
fec_roots=17: nbufs in [1, 3, 5, 15]
fec_roots=19: nbufs in [1, 229]
fec_roots=21: nbufs in [1, 3, 5, 13, 15, 39, 65, 195]
fec_roots=23: nbufs in [1, 89]
Regardless, fix it by refactoring how the parity blocks are read.