CVE-2026-89533 (GCVE-0-2026-89533)
Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-10-19 08:48
VLAI
EPSS
VEX
Title
svcrdma: Fix offset arithmetic in read_chunk_range
Summary
In the Linux kernel, the following vulnerability has been resolved:
svcrdma: Fix offset arithmetic in read_chunk_range
svc_rdma_read_chunk_range() walks a Read chunk's segment list to
build a sub-range starting at byte offset and spanning length bytes
for a Position-Zero or Call chunk. Two arithmetic defects in the
per-segment loop produce wrong DMA lengths and a u32 underflow:
pcl_for_each_segment(segment, chunk) {
if (offset > segment->rs_length) {
offset -= segment->rs_length;
continue;
}
dummy.rs_handle = segment->rs_handle;
dummy.rs_length = min_t(u32, length,
segment->rs_length) - offset;
dummy.rs_offset = segment->rs_offset + offset;
First, the skip predicate uses '>' instead of '>='. When offset
equals the segment's full rs_length, the segment is fully consumed
and should be skipped, but the loop falls through into the body.
The resulting dummy.rs_length is min_t(u32, length, rs_length) -
rs_length, which underflows to a near-UINT_MAX u32 when length is
smaller than rs_length, or is zero otherwise.
Second, the length formula subtracts offset from the min_t() result
rather than from segment->rs_length before the cap. For offset > 0
the segment's residual is rs_length - offset, not rs_length, so the
cap must be applied to the residual. With the current bracketing,
whenever length is smaller than rs_length - offset the per-segment
length becomes length - offset instead of length, silently dropping
offset bytes from the rebuilt chunk. Combined with the boundary
case above it also enables the u32 underflow path, which propagates
a huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB
kmalloc_array_node() in svc_rdma_get_rw_ctxt().
Additionally, svc_rdma_read_call_chunk() can invoke this function
with length == 0 when the last Read chunk ends exactly at the end
of the Call chunk. With the corrected >= predicate, every segment
is skipped and the function returns the initial -EINVAL, rejecting
a valid request. Return success immediately when length is zero.
Also break out of the loop once length is fully consumed to avoid
passing zero-length segments to svc_rdma_build_read_segment().
Fix by using '>=' so a fully-consumed segment is skipped, by
moving '- offset' inside min_t() so the cap is applied to the
segment's residual length, by returning success for zero-length
requests, and by stopping iteration when the requested range has
been consumed.
Severity
9.8 (Critical)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:23 UTC
Assigner
References
7 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < 10873311f91db9454e2fadbf9866bc819e0646d9
(git)
Affected: d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7 (git) Affected: d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < cba8543c18cf42fd80fd63effb6df6ff4f7e73ce (git) Affected: d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < 6ee4dc7476b3abc92ec1d444533a559f33f59561 (git) Affected: d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < a46b35f213c2426f5d6a0458a8f7e873fc59cdfd (git) Affected: d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < 4493c96bbd0068fadf69cbae8d13426202e34cdc (git) Affected: d7cc73972661be4a02a1b09f1d9b3283c6c05154 , < 4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e (git) |
guessed | |
| Linux | Linux |
Affected:
5.11
Unaffected: 0 , < 5.11 (semver) Unaffected: 5.15.221 , ≤ 5.15.* (semver) Unaffected: 6.1.188 , ≤ 6.1.* (semver) Unaffected: 6.6.157 , ≤ 6.6.* (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix) |
guessed |
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"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsvcrdma: Fix offset arithmetic in read_chunk_range\n\nsvc_rdma_read_chunk_range() walks a Read chunk\u0027s segment list to\nbuild a sub-range starting at byte offset and spanning length bytes\nfor a Position-Zero or Call chunk. Two arithmetic defects in the\nper-segment loop produce wrong DMA lengths and a u32 underflow:\n\n pcl_for_each_segment(segment, chunk) {\n if (offset \u003e segment-\u003ers_length) {\n offset -= segment-\u003ers_length;\n continue;\n }\n\n dummy.rs_handle = segment-\u003ers_handle;\n dummy.rs_length = min_t(u32, length,\n segment-\u003ers_length) - offset;\n dummy.rs_offset = segment-\u003ers_offset + offset;\n\nFirst, the skip predicate uses \u0027\u003e\u0027 instead of \u0027\u003e=\u0027. When offset\nequals the segment\u0027s full rs_length, the segment is fully consumed\nand should be skipped, but the loop falls through into the body.\nThe resulting dummy.rs_length is min_t(u32, length, rs_length) -\nrs_length, which underflows to a near-UINT_MAX u32 when length is\nsmaller than rs_length, or is zero otherwise.\n\nSecond, the length formula subtracts offset from the min_t() result\nrather than from segment-\u003ers_length before the cap. For offset \u003e 0\nthe segment\u0027s residual is rs_length - offset, not rs_length, so the\ncap must be applied to the residual. With the current bracketing,\nwhenever length is smaller than rs_length - offset the per-segment\nlength becomes length - offset instead of length, silently dropping\noffset bytes from the rebuilt chunk. Combined with the boundary\ncase above it also enables the u32 underflow path, which propagates\na huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB\nkmalloc_array_node() in svc_rdma_get_rw_ctxt().\n\nAdditionally, svc_rdma_read_call_chunk() can invoke this function\nwith length == 0 when the last Read chunk ends exactly at the end\nof the Call chunk. With the corrected \u003e= predicate, every segment\nis skipped and the function returns the initial -EINVAL, rejecting\na valid request. Return success immediately when length is zero.\nAlso break out of the loop once length is fully consumed to avoid\npassing zero-length segments to svc_rdma_build_read_segment().\n\nFix by using \u0027\u003e=\u0027 so a fully-consumed segment is skipped, by\nmoving \u0027- offset\u0027 inside min_t() so the cap is applied to the\nsegment\u0027s residual length, by returning success for zero-length\nrequests, and by stopping iteration when the requested range has\nbeen consumed."
}
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"value": "AV:N - svcrdma is nfsd\u0027s RPC-over-RDMA server transport; a remote peer reaches svc_rdma_read_chunk_range() by sending a Call with a Position-Zero/Call chunk and Read list over routable iWARP or RoCEv2, matching prior kernel CNA scores for this subsystem.\nAC:L - The attacker fully controls Call-chunk segment lengths and Read-chunk positions and can place a Read chunk on a segment boundary with a smaller remaining range so dummy.rs_length underflows a u32 deterministically, with no race or uncontrollable layout.\nPR:N - svc_rdma_process_read_list() runs in svc_rdma_recvfrom() while assembling the transport message, before svc_process() performs RPC or NFS authentication, and RDMA CM accept has no credential check.\nUI:N - Sending a crafted RPC-over-RDMA message with a malicious Call chunk and Read list to an already-listening NFS/RDMA service is sufficient; no victim mount, click, or other user action is required.\nS:U - The vulnerable NFS/RDMA service and affected kernel memory belong to the same host kernel security authority; this is not a VM, IOMMU, or sandbox escape.\nC:H - The underflowed length is added to rc_readbytes and, when Reads complete, svc_rdma_read_complete_pzrc() sets xdr_buf.page_len to a near-4GiB value, so XDR walks far past the rq_pages allocation and reads adjacent kernel heap as page pointers.\nI:H - XDR helpers such as xdr_buf_pages_zero() kmap and memset through that inflated page_len, writing via out-of-bounds page pointers taken from adjacent slab, a kernel integrity and control-flow hijack primitive.\nA:H - On the scatterlist path PAGE_ALIGN wrapping to 0 hits sg_alloc_table_chained(0) which BUG_ON(!nents) and panics; the huge page_len walk oopses on invalid pages, and an unauthenticated peer can repeat this per request."
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"title": "svcrdma: Fix offset arithmetic in read_chunk_range",
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"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsvcrdma: Fix offset arithmetic in read_chunk_range\n\nsvc_rdma_read_chunk_range() walks a Read chunk\u0027s segment list to\nbuild a sub-range starting at byte offset and spanning length bytes\nfor a Position-Zero or Call chunk. Two arithmetic defects in the\nper-segment loop produce wrong DMA lengths and a u32 underflow:\n\n pcl_for_each_segment(segment, chunk) {\n if (offset \u003e segment-\u003ers_length) {\n offset -= segment-\u003ers_length;\n continue;\n }\n\n dummy.rs_handle = segment-\u003ers_handle;\n dummy.rs_length = min_t(u32, length,\n segment-\u003ers_length) - offset;\n dummy.rs_offset = segment-\u003ers_offset + offset;\n\nFirst, the skip predicate uses \u0027\u003e\u0027 instead of \u0027\u003e=\u0027. When offset\nequals the segment\u0027s full rs_length, the segment is fully consumed\nand should be skipped, but the loop falls through into the body.\nThe resulting dummy.rs_length is min_t(u32, length, rs_length) -\nrs_length, which underflows to a near-UINT_MAX u32 when length is\nsmaller than rs_length, or is zero otherwise.\n\nSecond, the length formula subtracts offset from the min_t() result\nrather than from segment-\u003ers_length before the cap. For offset \u003e 0\nthe segment\u0027s residual is rs_length - offset, not rs_length, so the\ncap must be applied to the residual. With the current bracketing,\nwhenever length is smaller than rs_length - offset the per-segment\nlength becomes length - offset instead of length, silently dropping\noffset bytes from the rebuilt chunk. Combined with the boundary\ncase above it also enables the u32 underflow path, which propagates\na huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB\nkmalloc_array_node() in svc_rdma_get_rw_ctxt().\n\nAdditionally, svc_rdma_read_call_chunk() can invoke this function\nwith length == 0 when the last Read chunk ends exactly at the end\nof the Call chunk. With the corrected \u003e= predicate, every segment\nis skipped and the function returns the initial -EINVAL, rejecting\na valid request. Return success immediately when length is zero.\nAlso break out of the loop once length is fully consumed to avoid\npassing zero-length segments to svc_rdma_build_read_segment().\n\nFix by using \u0027\u003e=\u0027 so a fully-consumed segment is skipped, by\nmoving \u0027- offset\u0027 inside min_t() so the cap is applied to the\nsegment\u0027s residual length, by returning success for zero-length\nrequests, and by stopping iteration when the requested range has\nbeen consumed."
}
],
"id": "CVE-2026-89533",
"lastModified": "2026-10-19T09:17:47.923",
"metrics": {
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{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"cve": "CVE-2026-89533",
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"initial_release_date": "2026-09-11T00:00:00+00:00",
"product_status:known_affected": "237",
"product_status:known_not_affected": "42",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: svcrdma: Fix offset arithmetic in read_chunk_range",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89533.json",
"version": "3"
},
"vulnrichment": {
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"metrics": [
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"id": "CVE-2026-89533",
"options": [
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},
{
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},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T19:23:13.656876Z",
"version": "2.0.3"
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
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"product": "Linux",
"programFiles": [
"net/sunrpc/xprtrdma/svc_rdma_rw.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"versions": [
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"versions": [
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"version": "7.3",
"versionType": "original_commit_for_fix"
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"descriptions": [
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"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsvcrdma: Fix offset arithmetic in read_chunk_range\n\nsvc_rdma_read_chunk_range() walks a Read chunk\u0027s segment list to\nbuild a sub-range starting at byte offset and spanning length bytes\nfor a Position-Zero or Call chunk. Two arithmetic defects in the\nper-segment loop produce wrong DMA lengths and a u32 underflow:\n\n pcl_for_each_segment(segment, chunk) {\n if (offset \u003e segment-\u003ers_length) {\n offset -= segment-\u003ers_length;\n continue;\n }\n\n dummy.rs_handle = segment-\u003ers_handle;\n dummy.rs_length = min_t(u32, length,\n segment-\u003ers_length) - offset;\n dummy.rs_offset = segment-\u003ers_offset + offset;\n\nFirst, the skip predicate uses \u0027\u003e\u0027 instead of \u0027\u003e=\u0027. When offset\nequals the segment\u0027s full rs_length, the segment is fully consumed\nand should be skipped, but the loop falls through into the body.\nThe resulting dummy.rs_length is min_t(u32, length, rs_length) -\nrs_length, which underflows to a near-UINT_MAX u32 when length is\nsmaller than rs_length, or is zero otherwise.\n\nSecond, the length formula subtracts offset from the min_t() result\nrather than from segment-\u003ers_length before the cap. For offset \u003e 0\nthe segment\u0027s residual is rs_length - offset, not rs_length, so the\ncap must be applied to the residual. With the current bracketing,\nwhenever length is smaller than rs_length - offset the per-segment\nlength becomes length - offset instead of length, silently dropping\noffset bytes from the rebuilt chunk. Combined with the boundary\ncase above it also enables the u32 underflow path, which propagates\na huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB\nkmalloc_array_node() in svc_rdma_get_rw_ctxt().\n\nAdditionally, svc_rdma_read_call_chunk() can invoke this function\nwith length == 0 when the last Read chunk ends exactly at the end\nof the Call chunk. With the corrected \u003e= predicate, every segment\nis skipped and the function returns the initial -EINVAL, rejecting\na valid request. Return success immediately when length is zero.\nAlso break out of the loop once length is fully consumed to avoid\npassing zero-length segments to svc_rdma_build_read_segment().\n\nFix by using \u0027\u003e=\u0027 so a fully-consumed segment is skipped, by\nmoving \u0027- offset\u0027 inside min_t() so the cap is applied to the\nsegment\u0027s residual length, by returning success for zero-length\nrequests, and by stopping iteration when the requested range has\nbeen consumed."
}
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"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
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"value": "AV:N - svcrdma is nfsd\u0027s RPC-over-RDMA server transport; a remote peer reaches svc_rdma_read_chunk_range() by sending a Call with a Position-Zero/Call chunk and Read list over routable iWARP or RoCEv2, matching prior kernel CNA scores for this subsystem.\nAC:L - The attacker fully controls Call-chunk segment lengths and Read-chunk positions and can place a Read chunk on a segment boundary with a smaller remaining range so dummy.rs_length underflows a u32 deterministically, with no race or uncontrollable layout.\nPR:N - svc_rdma_process_read_list() runs in svc_rdma_recvfrom() while assembling the transport message, before svc_process() performs RPC or NFS authentication, and RDMA CM accept has no credential check.\nUI:N - Sending a crafted RPC-over-RDMA message with a malicious Call chunk and Read list to an already-listening NFS/RDMA service is sufficient; no victim mount, click, or other user action is required.\nS:U - The vulnerable NFS/RDMA service and affected kernel memory belong to the same host kernel security authority; this is not a VM, IOMMU, or sandbox escape.\nC:H - The underflowed length is added to rc_readbytes and, when Reads complete, svc_rdma_read_complete_pzrc() sets xdr_buf.page_len to a near-4GiB value, so XDR walks far past the rq_pages allocation and reads adjacent kernel heap as page pointers.\nI:H - XDR helpers such as xdr_buf_pages_zero() kmap and memset through that inflated page_len, writing via out-of-bounds page pointers taken from adjacent slab, a kernel integrity and control-flow hijack primitive.\nA:H - On the scatterlist path PAGE_ALIGN wrapping to 0 hits sg_alloc_table_chained(0) which BUG_ON(!nents) and panics; the huge page_len walk oopses on invalid pages, and an unauthenticated peer can repeat this per request."
}
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}
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"title": "svcrdma: Fix offset arithmetic in read_chunk_range",
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"cveId": "CVE-2026-89533",
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}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.