GHSA-JVQ3-FGQ9-MFPJ
Vulnerability from github – Published: 2026-04-22 15:31 – Updated: 2026-04-27 15:30In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN
The BPF interpreter's signed 32-bit division and modulo handlers use the kernel abs() macro on s32 operands. The abs() macro documentation (include/linux/math.h) explicitly states the result is undefined when the input is the type minimum. When DST contains S32_MIN (0x80000000), abs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged on arm64/x86. This value is then sign-extended to u64 as 0xFFFFFFFF80000000, causing do_div() to compute the wrong result.
The verifier's abstract interpretation (scalar32_min_max_sdiv) computes the mathematically correct result for range tracking, creating a verifier/interpreter mismatch that can be exploited for out-of-bounds map value access.
Introduce abs_s32() which handles S32_MIN correctly by casting to u32 before negating, avoiding signed overflow entirely. Replace all 8 abs((s32)...) call sites in the interpreter's sdiv32/smod32 handlers.
s32 is the only affected case -- the s64 division/modulo handlers do not use abs().
{
"affected": [],
"aliases": [
"CVE-2026-31525"
],
"database_specific": {
"cwe_ids": [
"CWE-787"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-22T14:16:52Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN\n\nThe BPF interpreter\u0027s signed 32-bit division and modulo handlers use\nthe kernel abs() macro on s32 operands. The abs() macro documentation\n(include/linux/math.h) explicitly states the result is undefined when\nthe input is the type minimum. When DST contains S32_MIN (0x80000000),\nabs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged\non arm64/x86. This value is then sign-extended to u64 as\n0xFFFFFFFF80000000, causing do_div() to compute the wrong result.\n\nThe verifier\u0027s abstract interpretation (scalar32_min_max_sdiv) computes\nthe mathematically correct result for range tracking, creating a\nverifier/interpreter mismatch that can be exploited for out-of-bounds\nmap value access.\n\nIntroduce abs_s32() which handles S32_MIN correctly by casting to u32\nbefore negating, avoiding signed overflow entirely. Replace all 8\nabs((s32)...) call sites in the interpreter\u0027s sdiv32/smod32 handlers.\n\ns32 is the only affected case -- the s64 division/modulo handlers do\nnot use abs().",
"id": "GHSA-jvq3-fgq9-mfpj",
"modified": "2026-04-27T15:30:40Z",
"published": "2026-04-22T15:31:44Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31525"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0d5d8c3ce45c734aaf3c51cbef59155a6746157d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/694ea55f1b1c74f9942d91ec366ae9e822422e42"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9ab1227765c446942f290c83382f0b19887c55cf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c77b30bd1dcb61f66c640ff7d2757816210c7cb0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f14ca604c0ff274fba19f73f1f0485c0047c1396"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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