CVE-2026-74256
HIGHCVE-2026-74256 is a high-severity (CVSS 8.4) remote code execution vulnerability in Kernel. O3 Security confirms whether CVE-2026-74256 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
bpf, sockmap: fix integer overflow in bpf_msg_pop_data() bounds check
Real-World Exposure
KernelReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Linux packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐧Linux | Kernel | ≥ 5.0.0&&< 5.10.261 | 5.10.261 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Kernel to 5.10.261 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-74256 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-74256 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-74256. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-74256 in your dependencies?
O3 detects CVE-2026-74256 across Linux dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.