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High severity7.8NVD Advisory· Published Sep 16, 2025· Updated May 12, 2026

CVE-2025-39835

CVE-2025-39835

Description

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

xfs: do not propagate ENODATA disk errors into xattr code

ENODATA (aka ENOATTR) has a very specific meaning in the xfs xattr code; namely, that the requested attribute name could not be found.

However, a medium error from disk may also return ENODATA. At best, this medium error may escape to userspace as "attribute not found" when in fact it's an IO (disk) error.

At worst, we may oops in xfs_attr_leaf_get() when we do:

error = xfs_attr_leaf_hasname(args, &bp); if (error == -ENOATTR) { xfs_trans_brelse(args->trans, bp); return error; }

because an ENODATA/ENOATTR error from disk leaves us with a null bp, and the xfs_trans_brelse will then null-deref it.

As discussed on the list, we really need to modify the lower level IO functions to trap all disk errors and ensure that we don't let unique errors like this leak up into higher xfs functions - many like this should be remapped to EIO.

However, this patch directly addresses a reported bug in the xattr code, and should be safe to backport to stable kernels. A larger-scope patch to handle more unique errors at lower levels can follow later.

(Note, prior to 07120f1abdff we did not oops, but we did return the wrong error code to userspace.)

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

In the Linux kernel, a disk medium error returning ENODATA can cause an oops or wrong error code in the XFS xattr code when the attribute is not found due to I/O failure.

Vulnerability

In the Linux kernel's XFS filesystem, the xattr (extended attribute) code can misinterpret an ENODATA (ENOATTR) error returned from a disk I/O operation. The ENODATA/ENOATTR error has a very specific meaning in the xattr code: the requested attribute name was not found. However, a medium error from disk can also return ENODATA. This confusion can cause the kernel to either propagate the wrong error code to userspace (reporting "attribute not found" instead of an I/O error), or worse, cause a null-pointer dereference (oops) in xfs_attr_leaf_get() when it attempts to release a buffer pointer that is NULL after the error [description].

Attack

Vector

The vulnerability occurs when a user or process attempts to access an extended attribute on an XFS filesystem, and the underlying disk returns a medium error that is represented as ENODATA. The attacker needs to have the ability to cause such a disk error (e.g., by inducing physical media corruption or by using a faulty storage device) and then trigger an xattr lookup. No special privileges beyond normal file access are required, because the xattr operations are performed during normal filesystem usage. The erroneous error propagation can be triggered from userspace by an unprivileged user accessing extended attributes on a filesystem experiencing disk errors [description].

Impact

The most severe consequence is a kernel oops (null-pointer dereference), which causes a denial of service (system crash). In less severe cases, the kernel returns an incorrect error code (ENOATTR instead of EIO) to the user, potentially masking underlying hardware failures and leading to incorrect application behavior. This vulnerability does not allow privilege escalation or arbitrary code execution, but it can lead to system instability and incorrect error handling [description].

Mitigation

The patch directly addresses the bug in the xattr code by ensuring that disk errors are not propagated as ENOATTR. The fix has been committed to the Linux kernel stable tree, and backports are expected to be safe for stable kernels [description]. Affected users should apply the updated kernel from their distribution when available. The Siemens advisory lists this CVE (along with many others) as affecting SIMATIC CN 4100 devices, referencing the underlying kernel fix [1].

References
  1. SSA-032379

AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

2

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

10

News mentions

1