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CVE Record

CVE-2025-71074: functionfs: fix the open/removal races

In the Linux kernel, the following vulnerability has been resolved: functionfs: fix the open/removal races ffs_epfile_open() can race with removal, ending up with file->private_data pointing to freed object. There is a total count of opened files on functionfs (both ep0 and dynamic ones) and when it hits zero, dynamic files get removed. Unfortunately, that removal can happen while another thread is in ffs_epfile_open(), but has not incremented the count yet. In that case open will succeed, leaving us with UAF on any subsequent read() or write(). The root cause is that ffs->opened is misused; atomic_dec_and_test() vs. atomic_add_return() is not a good idea, when object remains visible all along. To untangle that * serialize openers on ffs->mutex (both for ep0 and for dynamic files) * have dynamic ones use atomic_inc_not_zero() and fail if we had zero ->opened; in that case the file we are opening is doomed. * have the inodes of dynamic files marked on removal (from the callback of simple_recursive_removal()) - clear ->i_private there. * have open of dynamic ones verify they hadn't been already removed, along with checking that state is FFS_ACTIVE.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A local user can trigger a race while Linux FunctionFS endpoint files are being opened and removed. A successful race leaves the kernel using freed memory during later reads or writes, potentially enabling data exposure, corruption, or system compromise. The supplied CVSS score is 7.8, but exposure depends on FunctionFS use and local access.

Executive priority

Prioritize affected multi-user, appliance, or embedded systems where untrusted users can access FunctionFS. Treat remediation as high priority because successful exploitation may compromise the kernel, but avoid assuming fleet-wide exposure until FunctionFS usage and vendor patch status are verified.

Technical view

ffs_epfile_open() may race with dynamic-file removal before the open-file count is incremented, leaving file->private_data referencing freed memory. Subsequent read or write operations can cause a use-after-free. The kernel fix serializes opens, prevents count resurrection, marks removed inodes, and verifies inode presence and FFS_ACTIVE state.

Likely exposure

Potentially exposed systems run an affected Linux kernel, use FunctionFS, and permit a low-privileged local user to interact with relevant endpoint files. The supplied version data identifies Linux 2.6.35 through 6.19 as affected, but downstream vendor backports may change actual status.

Exploitation context

The CVSS vector describes local, low-complexity exploitation requiring low privileges and no user interaction, with potentially high confidentiality, integrity, and availability impact. The CVE is not listed as KEV in the supplied bundle, and no cited source establishes active exploitation or public weaponization.

Researcher notes

The flaw is an open-versus-removal lifetime race involving ffs->opened, dynamic inode removal, and file->private_data. The source describes a deterministic correction strategy but provides no exploitation evidence. The supplied affected-version range is broad and should be reconciled against stable-tree and distribution backport records.

Mitigation direction

  • Identify systems using FunctionFS and prioritize those accessible to untrusted local users.
  • Apply a vendor-supported kernel containing the referenced FunctionFS race fix.
  • Check distribution advisories because kernel fixes may be backported without matching upstream version numbers.
  • Restrict unnecessary local access to FunctionFS endpoint files while updates are pending.

Validation and detection

  • Record running kernel versions and compare them with vendor security advisories.
  • Confirm whether FunctionFS is enabled and actively used on each system.
  • Verify the installed kernel includes the referenced upstream fix or an equivalent vendor backport.
  • Reassess local permissions protecting FunctionFS endpoint files after remediation.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-71074 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-71074Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxddf8abd2599491cbad959c700b90ba72a5dce8d0unaffected
LinuxLinux2.6.35, 0, 6.19affected
Weakness

CWE details

No CWE listed

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