GHSA-G75R-RWJF-JP26
Vulnerability from github – Published: 2026-10-23 15:31 – Updated: 2026-10-23 15:31In the Linux kernel, the following vulnerability has been resolved:
net/sched: em_text: reject unterminated algo before autoload
This is a follow-up to commit 9c572a83037a ("net/sched: fix potential stack infoleak in em_text_dump()"), which zero-initialised the dump-side struct. Sashiko pointed at a pre-existing bug that exposed the change-side input-validation gap open.
em_text_change() casts the raw netlink attribute payload to struct tcf_em_text and passes conf->algo, a 16-byte array with no enforced NUL terminator, to textsearch_prepare(). On the TS_AUTOLOAD retry textsearch_prepare() calls request_module("ts_%s", algo); vsnprintf() walks %s until it finds a NUL, so an algo[] with no NUL reads past the array into the adjacent struct fields and payload and feeds those bytes to the usermode helper command line. This is an out-of-bounds read and a kernel memory disclosure.
Reject the attribute when no NUL exists within TC_EM_TEXT_ALGOSIZ bytes, matching the check xt_string has had since 3ab720881b6e.
Conditions to recreate the bug: - CAP_NET_ADMIN on the target netns (namespace-local via unshare -Urn is enough) - install clsact on an interface, then add a basic filter with one text ematch whose algo[] is 16 bytes with no NUL (e.g. "A"*16) and pattern_len at least 1 - the add fails with -ENOENT and the kernel invokes modprobe with a module name made of "ts_" plus the 16 bytes and the adjacent payload
{
"affected": [],
"aliases": [
"CVE-2026-98969"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-23T13:17:18Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: em_text: reject unterminated algo before autoload\n\nThis is a follow-up to commit 9c572a83037a (\"net/sched: fix potential\nstack infoleak in em_text_dump()\"), which zero-initialised the dump-side\nstruct. Sashiko pointed at a pre-existing bug that exposed the change-side\ninput-validation gap open.\n\nem_text_change() casts the raw netlink attribute payload to struct\ntcf_em_text and passes conf-\u003ealgo, a 16-byte array with no enforced NUL\nterminator, to textsearch_prepare(). On the TS_AUTOLOAD retry\ntextsearch_prepare() calls request_module(\"ts_%s\", algo); vsnprintf()\nwalks %s until it finds a NUL, so an algo[] with no NUL reads past the\narray into the adjacent struct fields and payload and feeds those bytes\nto the usermode helper command line. This is an out-of-bounds read and\na kernel memory disclosure.\n\nReject the attribute when no NUL exists within TC_EM_TEXT_ALGOSIZ bytes,\nmatching the check xt_string has had since 3ab720881b6e.\n\nConditions to recreate the bug:\n- CAP_NET_ADMIN on the target netns (namespace-local via unshare -Urn\n is enough)\n- install clsact on an interface, then add a basic filter with one text\n ematch whose algo[] is 16 bytes with no NUL (e.g. \"A\"*16) and\n pattern_len at least 1\n- the add fails with -ENOENT and the kernel invokes modprobe with a\n module name made of \"ts_\" plus the 16 bytes and the adjacent payload",
"id": "GHSA-g75r-rwjf-jp26",
"modified": "2026-10-23T15:31:33Z",
"published": "2026-10-23T15:31:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98969"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/00bcc303000bac524d62eed054d77372b38ace0f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/22182f91c6703af6e9832cffe6d22b381031cb5a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/85e5512369d4fe6e5f2c43712d9f9e01d4ae8437"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b627c6ba20be20334338229b4820baacb9d96826"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c9728fcf2e7fb4a7a8d08ebd9524c3b02ae1a021"
}
],
"schema_version": "1.4.0",
"severity": []
}
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