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CVE-2024-49889

Status: ModifiedHigh (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

ext4: avoid use-after-free in ext4_ext_show_leaf()

In ext4_find_extent(), path may be freed by error or be reallocated, so using a previously saved *ppath may have been freed and thus may trigger use-after-free, as follows:

Similar to ext4_split_extent_at(), we use *ppath directly as an input to ext4_ext_show_leaf(). Fix a spelling error by the way.

Same problem in ext4_ext_handle_unwritten_extents(). Since 'path' is only used in ext4_ext_show_leaf(), remove 'path' and use *ppath directly.

This issue is triggered only when EXT_DEBUG is defined and therefore does not affect functionality.

Technical details traces, logs and code from the original report
ext4_split_extent
  path = *ppath;
  ext4_split_extent_at(ppath)
  path = ext4_find_extent(ppath)
  ext4_split_extent_at(ppath)
    // ext4_find_extent fails to free path
    // but zeroout succeeds
  ext4_ext_show_leaf(inode, path)
    eh = path[depth].p_hdr
    // path use-after-free !!!

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

Vulnerabilidad de use-after-free (CWE-416) en kernel Linux con acceso local (AV:L) y privilegios de usuario (PR:L) sin interacción. Permite ejecución de código con elevación de privilegios desde contexto local.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Execution PreventionThreat Intelligence ProgramRestrict Web-Based ContentPrivileged Account ManagementLimit Software InstallationBehavior Prevention on Endpoint

Affected technologies (1)

Linux — Linux Kernel

CWEs

References

Raw JSON (NVD)

Show
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: avoid use-after-free in ext4_ext_show_leaf()\n\nIn ext4_find_extent(), path may be freed by error or be reallocated, so\nusing a previously saved *ppath may have been freed and thus may trigger\nuse-after-free, as follows:\n\next4_split_extent\n  path = *ppath;\n  ext4_split_extent_at(ppath)\n  path = ext4_find_extent(ppath)\n  ext4_split_extent_at(ppath)\n    // ext4_find_extent fails to free path\n    // but zeroout succeeds\n  ext4_ext_show_leaf(inode, path)\n    eh = path[depth].p_hdr\n    // path use-after-free !!!\n\nSimilar to ext4_split_extent_at(), we use *ppath directly as an input to\next4_ext_show_leaf(). Fix a spelling error by the way.\n\nSame problem in ext4_ext_handle_unwritten_extents(). Since 'path' is only\nused in ext4_ext_show_leaf(), remove 'path' and use *ppath directly.\n\nThis issue is triggered only when EXT_DEBUG is defined and therefore does\nnot affect functionality."
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      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ext4: evitar use after free en ext4_ext_show_leaf() En ext4_find_extent(), path puede liberarse por error o reasignarse, por lo que el uso de un *ppath previamente guardado puede haberse liberado y, por lo tanto, puede activar el use after free, de la siguiente manera: ext4_split_extent path = *ppath; ext4_split_extent_at(ppath) path = ext4_find_extent(ppath) ext4_split_extent_at(ppath) // ext4_find_extent no puede liberar path // pero la puesta a cero tiene éxito ext4_ext_show_leaf(inode, path) eh = path[depth].p_hdr // use after free de path !!! De manera similar a ext4_split_extent_at(), usamos *ppath directamente como entrada para ext4_ext_show_leaf(). Por cierto, corrige un error ortográfico. El mismo problema en ext4_ext_handle_unwritten_extents(). Dado que 'path' solo se usa en ext4_ext_show_leaf(), elimine 'path' y use *ppath directamente. Este problema se activa solo cuando se define EXT_DEBUG y, por lo tanto, no afecta la funcionalidad."
    }
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