CVE-2026-74256 (GCVE-0-2026-74256)
Vulnerability from cvelistv5
Published
2026-08-15 05:57
Modified
2026-08-17 05:45
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
bpf, sockmap: fix integer overflow in bpf_msg_pop_data() bounds check
start and len are u32, so
u64 last = start + len;
evaluates start + len in 32-bit and wraps before storing it in last.
The bounds check
if (start >= offset + l || last > msg->sg.size)
return -EINVAL;
can then be passed with an out-of-range start/len, after which the pop
loop runs off the end of the scatterlist and sk_msg_shift_left() calls
put_page() on the empty msg->sg.end slot:
Oops: general protection fault, probably for non-canonical address
0xdffffc0000000001: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
RIP: 0010:sk_msg_shift_left net/core/filter.c:2957 [inline]
RIP: 0010:____bpf_msg_pop_data net/core/filter.c:3103 [inline]
RIP: 0010:bpf_msg_pop_data+0x753/0x1a10 net/core/filter.c:2984
Call Trace:
<TASK>
bpf_prog_4cc92c278f4d5d56+0x1b1/0x1e8
bpf_prog_run_pin_on_cpu+0x107/0x320 include/linux/filter.h:746
sk_psock_msg_verdict+0x357/0x7f0 net/core/skmsg.c:934
tcp_bpf_send_verdict net/ipv4/tcp_bpf.c:420 [inline]
tcp_bpf_sendmsg+0x766/0x1ae0 net/ipv4/tcp_bpf.c:583
__sock_sendmsg+0x153/0x1c0 net/socket.c:802
__sys_sendto+0x326/0x430 net/socket.c:2265
__x64_sys_sendto+0xe3/0x100 net/socket.c:2268
do_syscall_64+0x14c/0x480
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
Widen the addition with a (u64) cast so the bound is evaluated in
64-bit and a len near U32_MAX no longer wraps below msg->sg.size.
While here, change pop from int to u32. It counts bytes against the
unsigned scatterlist lengths and can never be negative, so the signed
type only invites sign-confusion in the pop loop.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 Version: 7246d8ed4dcce23f7509949a77be15fa9f0e3d28 |
||
{
"containers": {
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],
"cpeApplicability": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf, sockmap: fix integer overflow in bpf_msg_pop_data() bounds check\n\nstart and len are u32, so\n\n\tu64 last = start + len;\n\nevaluates start + len in 32-bit and wraps before storing it in last.\nThe bounds check\n\n\tif (start \u003e= offset + l || last \u003e msg-\u003esg.size)\n\t\treturn -EINVAL;\n\ncan then be passed with an out-of-range start/len, after which the pop\nloop runs off the end of the scatterlist and sk_msg_shift_left() calls\nput_page() on the empty msg-\u003esg.end slot:\n\n Oops: general protection fault, probably for non-canonical address\n 0xdffffc0000000001: 0000 [#1] SMP KASAN PTI\n KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]\n RIP: 0010:sk_msg_shift_left net/core/filter.c:2957 [inline]\n RIP: 0010:____bpf_msg_pop_data net/core/filter.c:3103 [inline]\n RIP: 0010:bpf_msg_pop_data+0x753/0x1a10 net/core/filter.c:2984\n Call Trace:\n \u003cTASK\u003e\n bpf_prog_4cc92c278f4d5d56+0x1b1/0x1e8\n bpf_prog_run_pin_on_cpu+0x107/0x320 include/linux/filter.h:746\n sk_psock_msg_verdict+0x357/0x7f0 net/core/skmsg.c:934\n tcp_bpf_send_verdict net/ipv4/tcp_bpf.c:420 [inline]\n tcp_bpf_sendmsg+0x766/0x1ae0 net/ipv4/tcp_bpf.c:583\n __sock_sendmsg+0x153/0x1c0 net/socket.c:802\n __sys_sendto+0x326/0x430 net/socket.c:2265\n __x64_sys_sendto+0xe3/0x100 net/socket.c:2268\n do_syscall_64+0x14c/0x480\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n \u003c/TASK\u003e\n\nWiden the addition with a (u64) cast so the bound is evaluated in\n64-bit and a len near U32_MAX no longer wraps below msg-\u003esg.size.\n\nWhile here, change pop from int to u32. It counts bytes against the\nunsigned scatterlist lengths and can never be negative, so the signed\ntype only invites sign-confusion in the pop loop."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.4,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The flaw is in the BPF sk_msg helper bpf_msg_pop_data(), reached only from the sockmap egress verdict path via local sendmsg/sendto on a sockmap- or kTLS-attached socket (tcp_bpf_sendmsg/tls_sw_sendmsg \u2192 sk_psock_msg_verdict), matching kernel CNA BPF/sockmap Local guidance.\nAC:L - start and len are ARG_ANYTHING (verifier unbounded); an sk_msg program can pick values whose u32 sum wraps below msg-\u003esg.size (e.g. start=100, len\u2248U32_MAX) and trigger the bad path deterministically with a single sendmsg, with no race or external state.\nPR:N - Triggering corruption requires only sendmsg on a socket already in a sockmap whose SK_MSG program calls bpf_msg_pop_data; on internet-facing kTLS/sockmap L7 proxies an unauthenticated remote client can reach this with no victim credentials, and arg2/arg3 are unconstrained by the verifier.\nUI:N - Exploitation needs only the attacker\u0027s own socket traffic and BPF-driven pop parameters; no independent victim mount, file open, or administrator action is required at trigger time.\nS:U - Out-of-bounds scatterlist manipulation corrupts kernel sk_msg/page state within the same kernel security authority and does not by itself cross VM, IOMMU, or hypervisor boundaries.\nC:H - After the overflowed bound check, sk_msg_shift_left() walks past msg-\u003esg.end, reading invalid scatterlist slots and dereferencing bogus page pointers via put_page(), yielding out-of-bounds kernel memory disclosure convertible to arbitrary read.\nI:H - The same over-run writes msg-\u003esg.data[] entries and copy bitmap state beyond the fixed MAX_MSG_FRAGS ring, corrupting adjacent kernel objects with attacker-influenced scatterlist metadata suitable for control-flow hijack and privilege escalation.\nA:H - The fix commit\u0027s KASAN trace shows a general protection fault/null-ptr-deref in sk_msg_shift_left() during bpf_msg_pop_data(); this reliably oopses the host and can panic even when full exploitation is not attempted."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:45:05.356Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/9ef44ed6fb0c1db01cfcc3de432a33e719713eb5"
},
{
"url": "https://git.kernel.org/stable/c/d693c5ed67dabe1ccbf8dcea93075bdc9ffd4ca0"
},
{
"url": "https://git.kernel.org/stable/c/ba5cc05dae8fce237d191c7ea96b1107a791e548"
},
{
"url": "https://git.kernel.org/stable/c/c05a0ec1cdced622a1a0c7d85679fe02f31033ec"
},
{
"url": "https://git.kernel.org/stable/c/17eb9832a10db2f7a80cb429ca2bc5038445a943"
},
{
"url": "https://git.kernel.org/stable/c/fe09dd288722f1c749b7506c0b3e7841a7d85027"
},
{
"url": "https://git.kernel.org/stable/c/e09f7bd7273928b4089e6b71f8e992f2b356ca1b"
},
{
"url": "https://git.kernel.org/stable/c/a48802fb2cd2d1e23651989f8ff4d15e9d5dad54"
}
],
"title": "bpf, sockmap: fix integer overflow in bpf_msg_pop_data() bounds check",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74256",
"datePublished": "2026-08-15T05:57:34.956Z",
"dateReserved": "2026-08-15T05:44:03.876Z",
"dateUpdated": "2026-08-17T05:45:05.356Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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