CVE-2025-39748
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
bpf: Forget ranges when refining tnum after JSET
Syzbot reported a kernel warning due to a range invariant violation on the following BPF program.
The issue is on the path where we fall through both jumps.
That path is unreachable at runtime: after insn 1, we know r0 != 0, but with the sign extension on the jset, we would only fallthrough insn 2 if r0 == 0. Unfortunately, is_branch_taken() isn't currently able to figure this out, so the verifier walks all branches. The verifier then refines the register bounds using the second condition and we end up with inconsistent bounds on this unreachable path:
Leer descripción completaMostrar menos
Improving the range refinement for JSET to cover all cases is tricky. We also don't expect many users to rely on JSET given LLVM doesn't generate those instructions. So instead of improving the range refinement for JSETs, Eduard suggested we forget the ranges whenever we're narrowing tnums after a JSET. This patch implements that approach.
Detalles técnicos trazas, registros y código del informe original
0: call bpf_get_netns_cookie
1: if r0 == 0 goto <exit>
2: if r0 & Oxffffffff goto <exit>
1: if r0 == 0 goto <exit>
r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff)
2: if r0 & 0xffffffff goto <exit>
r0 before reg_bounds_sync: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0)
r0 after reg_bounds_sync: u64=[0x1, 0] var_off=(0, 0)CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.17%
- Percentil entre todas las CVEs puntuadas: 6
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
CWE
- NVD-CWE-noinfo
Referencias
- https://git.kernel.org/stable/c/0643aa2468192a4d81326e8e76543854870b1ee2
- https://git.kernel.org/stable/c/22191359f8454b0be082c3b126f86bcbea0f1318
- https://git.kernel.org/stable/c/2fd0c26bacd90ef26522bd3169000a4715bf151f
- https://git.kernel.org/stable/c/591c788d16046edb0220800bf1819554af5853ce
- https://git.kernel.org/stable/c/6279846b9b2532e1b04559ef8bd0dec049f29383
- https://git.kernel.org/stable/c/80a6b11862a7cfdf691e8f9faee89cfea219f098
- https://git.kernel.org/stable/c/c29dd8336236a4deb75596b52d2dd16ccc4a380d
- https://git.kernel.org/stable/c/f01e06930444cab289a8783017af9b64255bd103
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Forget ranges when refining tnum after JSET\n\nSyzbot reported a kernel warning due to a range invariant violation on\nthe following BPF program.\n\n 0: call bpf_get_netns_cookie\n 1: if r0 == 0 goto <exit>\n 2: if r0 & Oxffffffff goto <exit>\n\nThe issue is on the path where we fall through both jumps.\n\nThat path is unreachable at runtime: after insn 1, we know r0 != 0, but\nwith the sign extension on the jset, we would only fallthrough insn 2\nif r0 == 0. Unfortunately, is_branch_taken() isn't currently able to\nfigure this out, so the verifier walks all branches. The verifier then\nrefines the register bounds using the second condition and we end\nup with inconsistent bounds on this unreachable path:\n\n 1: if r0 == 0 goto <exit>\n r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff)\n 2: if r0 & 0xffffffff goto <exit>\n r0 before reg_bounds_sync: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0)\n r0 after reg_bounds_sync: u64=[0x1, 0] var_off=(0, 0)\n\nImproving the range refinement for JSET to cover all cases is tricky. We\nalso don't expect many users to rely on JSET given LLVM doesn't generate\nthose instructions. So instead of improving the range refinement for\nJSETs, Eduard suggested we forget the ranges whenever we're narrowing\ntnums after a JSET. This patch implements that approach."
}
],
"lastModified": "2026-07-14T13:17:48.567",
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