CVE-2025-39748 (GCVE-0-2025-39748)
Vulnerability from cvelistv5
Published
2025-09-11 16:52
Modified
2025-09-11 16:52
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
0: call bpf_get_netns_cookie
1: if r0 == 0 goto <exit>
2: if r0 & Oxffffffff goto <exit>
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:
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)
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.
References
Impacted products
{
"containers": {
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"affected": [
{
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"product": "Linux",
"programFiles": [
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{
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{
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"versionType": "git"
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]
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"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.43",
"versionType": "semver"
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{
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"status": "unaffected",
"version": "6.15.11",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "6.16.2",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "6.17-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
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"descriptions": [
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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 \u003cexit\u003e\n 2: if r0 \u0026 Oxffffffff goto \u003cexit\u003e\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\u0027t 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 \u003cexit\u003e\n r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff)\n 2: if r0 \u0026 0xffffffff goto \u003cexit\u003e\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\u0027t expect many users to rely on JSET given LLVM doesn\u0027t generate\nthose instructions. So instead of improving the range refinement for\nJSETs, Eduard suggested we forget the ranges whenever we\u0027re narrowing\ntnums after a JSET. This patch implements that approach."
}
],
"providerMetadata": {
"dateUpdated": "2025-09-11T16:52:20.534Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"references": [
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"url": "https://git.kernel.org/stable/c/f01e06930444cab289a8783017af9b64255bd103"
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{
"url": "https://git.kernel.org/stable/c/2fd0c26bacd90ef26522bd3169000a4715bf151f"
},
{
"url": "https://git.kernel.org/stable/c/80a6b11862a7cfdf691e8f9faee89cfea219f098"
},
{
"url": "https://git.kernel.org/stable/c/6279846b9b2532e1b04559ef8bd0dec049f29383"
}
],
"title": "bpf: Forget ranges when refining tnum after JSET",
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"cveId": "CVE-2025-39748",
"datePublished": "2025-09-11T16:52:20.534Z",
"dateReserved": "2025-04-16T07:20:57.125Z",
"dateUpdated": "2025-09-11T16:52:20.534Z",
"state": "PUBLISHED"
},
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"nvd": "{\"cve\":{\"id\":\"CVE-2025-39748\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-09-11T17:15:38.237\",\"lastModified\":\"2025-09-15T15:22:38.297\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"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 \u003cexit\u003e\\n 2: if r0 \u0026 Oxffffffff goto \u003cexit\u003e\\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\u0027t 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 \u003cexit\u003e\\n r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff)\\n 2: if r0 \u0026 0xffffffff goto \u003cexit\u003e\\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\u0027t expect many users to rely on JSET given LLVM doesn\u0027t generate\\nthose instructions. So instead of improving the range refinement for\\nJSETs, Eduard suggested we forget the ranges whenever we\u0027re narrowing\\ntnums after a JSET. This patch implements that approach.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2fd0c26bacd90ef26522bd3169000a4715bf151f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6279846b9b2532e1b04559ef8bd0dec049f29383\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/80a6b11862a7cfdf691e8f9faee89cfea219f098\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f01e06930444cab289a8783017af9b64255bd103\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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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.
- 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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