CVE-2026-89544
Estado: RecibidaAlta (7.5)—
In the Linux kernel, the following vulnerability has been resolved:
SUNRPC: fix gssx_dec_option_array error path bugs
Four coupled defects in the gssx XDR option-array decoder make the error paths unsafe: a NULL deref in the caller, a refcount leak on the decoded group_info, and a latent use-after-free that the leak fix would otherwise expose.
gssx_dec_option_array() sets oa->count = 1 before allocating oa->data. If that allocation fails, -ENOMEM is returned with oa->count == 1 and oa->data == NULL. All other error paths jump to free_oa: which frees oa->data and NULLs it but also leaves oa->count == 1. The caller trusts the count:
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Independently, free_creds: releases the partially decoded svc_cred with a bare kfree(creds). gssx_dec_linux_creds() installs a groups_alloc() result into creds->cr_group_info; that object is kvmalloc-backed and refcounted, and only put_group_info() reaches kvfree(). A plain kfree(creds) drops the wrapper and leaks the group_info allocation.
The natural fix for the leak is to call free_svc_cred(creds) before kfree(creds), but free_svc_cred() invokes put_group_info() on creds->cr_group_info unconditionally when non-NULL. The existing out_free_groups: path in gssx_dec_linux_creds() already called groups_free() on that pointer without clearing it, so once free_svc_cred() is wired in, the subsequent put_group_info() would touch freed memory.
Fix all four together:
Detalles técnicos trazas, registros y código del informe original
gssp_accept_sec_context_upcall()
gssx_dec_accept_sec_context()
gssx_dec_option_array() /* fails, count=1 data=NULL */
data = res.options.data[0].value /* NULL deref */
- Move the oa->count = 1 assignment below the oa->data allocation
so it is never set when oa->data is NULL.
- Reset oa->count to 0 at free_oa: so count and data stay
coherent and the caller sees an empty option array.
- Call free_svc_cred(creds) before kfree(creds) at free_creds:
so the refcounted cr_group_info is released. free_svc_cred()
either NULL-guards each field explicitly (cr_group_info has
an if() check) or delegates to a helper that is NULL-safe
itself (kfree for the string fields, gss_mech_put() which
guards with if(gm) at gss_mech_switch.c:342), so it is safe
to call on a partially decoded svc_cred where only
cr_uid/cr_gid/cr_group_info have been written and everything
else is zero from kzalloc.
- In gssx_dec_linux_creds()'s out_free_groups: path, release
cr_group_info with put_group_info() rather than groups_free()
so the teardown matches free_svc_cred()'s refcount-aware path,
and clear the pointer so a later free_svc_cred() on the same
creds does not release it a second time.CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 7.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.59%
- Percentil entre todas las CVEs puntuadas: 47
- Fecha de la puntuación: 6/10/2026
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).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1190Exploit Public-Facing Applicationinitial access60 % - Impacto principal
T1499Endpoint Denial of Serviceimpact55 %
Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-89544",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.5,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "NONE",
"confidentialityImpact": "NONE"
},
"impactScore": 3.6,
"exploitabilityScore": 3.9
}
]
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
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"vendor": "Linux",
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{
"status": "affected",
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"lessThan": "6.8",
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{
"status": "affected",
"version": "6.8.2",
"lessThan": "6.9",
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],
"programFiles": [
"net/sunrpc/auth_gss/gss_rpc_xdr.c"
],
"defaultStatus": "unaffected"
},
{
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"vendor": "Linux",
"product": "Linux",
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"version": "6.9"
},
{
"status": "unaffected",
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{
"status": "unaffected",
"version": "6.12.111",
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]
}
],
"published": "2026-09-11T20:19:37.670",
"references": [
{
"url": "https://git.kernel.org/stable/c/3ff45361e9469e85c0f86b8e7b82c63e50bab8ef",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: fix gssx_dec_option_array error path bugs\n\nFour coupled defects in the gssx XDR option-array decoder make the\nerror paths unsafe: a NULL deref in the caller, a refcount leak on\nthe decoded group_info, and a latent use-after-free that the leak\nfix would otherwise expose.\n\ngssx_dec_option_array() sets oa->count = 1 before allocating\noa->data. If that allocation fails, -ENOMEM is returned with\noa->count == 1 and oa->data == NULL. All other error paths jump\nto free_oa: which frees oa->data and NULLs it but also leaves\noa->count == 1. The caller trusts the count:\n\n gssp_accept_sec_context_upcall()\n gssx_dec_accept_sec_context()\n gssx_dec_option_array() /* fails, count=1 data=NULL */\n data = res.options.data[0].value /* NULL deref */\n\nIndependently, free_creds: releases the partially decoded svc_cred\nwith a bare kfree(creds). gssx_dec_linux_creds() installs a\ngroups_alloc() result into creds->cr_group_info; that object is\nkvmalloc-backed and refcounted, and only put_group_info() reaches\nkvfree(). A plain kfree(creds) drops the wrapper and leaks the\ngroup_info allocation.\n\nThe natural fix for the leak is to call free_svc_cred(creds) before\nkfree(creds), but free_svc_cred() invokes put_group_info() on\ncreds->cr_group_info unconditionally when non-NULL. The existing\nout_free_groups: path in gssx_dec_linux_creds() already called\ngroups_free() on that pointer without clearing it, so once\nfree_svc_cred() is wired in, the subsequent put_group_info() would\ntouch freed memory.\n\nFix all four together:\n\n - Move the oa->count = 1 assignment below the oa->data allocation\n so it is never set when oa->data is NULL.\n - Reset oa->count to 0 at free_oa: so count and data stay\n coherent and the caller sees an empty option array.\n - Call free_svc_cred(creds) before kfree(creds) at free_creds:\n so the refcounted cr_group_info is released. free_svc_cred()\n either NULL-guards each field explicitly (cr_group_info has\n an if() check) or delegates to a helper that is NULL-safe\n itself (kfree for the string fields, gss_mech_put() which\n guards with if(gm) at gss_mech_switch.c:342), so it is safe\n to call on a partially decoded svc_cred where only\n cr_uid/cr_gid/cr_group_info have been written and everything\n else is zero from kzalloc.\n - In gssx_dec_linux_creds()'s out_free_groups: path, release\n cr_group_info with put_group_info() rather than groups_free()\n so the teardown matches free_svc_cred()'s refcount-aware path,\n and clear the pointer so a later free_svc_cred() on the same\n creds does not release it a second time."
}
],
"lastModified": "2026-09-21T14:17:22.970",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}