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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"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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{
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"published": "2026-09-11T20:19:36.250",
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"redhat_vex": {
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"current_release_date": "2026-11-07T04:39:32+00:00",
"cve": "CVE-2026-89533",
"id": "CVE-2026-89533",
"initial_release_date": "2026-09-11T00:00:00+00:00",
"product_status:known_affected": "161",
"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": {
"containers": {
"adp": [
{
"metrics": [
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"content": {
"id": "CVE-2026-89533",
"options": [
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},
{
"Automatable": "yes"
},
{
"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": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/sunrpc/xprtrdma/svc_rdma_rw.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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{
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"descriptions": [
{
"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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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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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.