Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2025-40205: btrfs: avoid potential out-of-bounds in btrfs_encode_fh()

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.15% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 0276c8582488022f057b4cec21975a5edf079f47, 361d67276eb8ec6be8f27f4ad6c6090459438fee, 43143776b0a7604d873d1a6f3e552a00aa930224; azl3 kernel 6.6.112.1-2 on Azure Linux 3.0 6.6.117.1-1.

Low priority for now. Upgrade to Linux Linux 0276c8582488022f057b4cec21975a5edf079f47, 361d67276eb8ec6be8f27f4ad6c6090459438fee, 43143776b0a7604d873d1a6f3e552a00aa930224; azl3 kernel 6.6.112.1-2 on Azure Linux 3.0 6.6.117.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: btrfs: avoid potential out-of-bounds in btrfs_encode_fh() The function btrfs_encode_fh() does not properly account for the three cases it handles. Before writing to the file handle (fh), the function only returns to the user BTRFS_FID_SIZE_NON_CONNECTABLE (5 dwords, 20 bytes) or BTRFS_FID_SIZE_CONNECTABLE (8 dwords, 32 bytes). However, when a parent exists and the root ID of the parent and the inode are different, the function writes BTRFS_FID_SIZE_CONNECTABLE_ROOT (10 dwords, 40 bytes). If *max_len is not large enough, this write goes out of bounds because BTRFS_FID_SIZE_CONNECTABLE_ROOT is greater than BTRFS_FID_SIZE_CONNECTABLE originally returned. This results in an 8-byte out-of-bounds write at fid->parent_root_objectid = parent_root_id. A previous attempt to fix this issue was made but was lost. https://lore.kernel.org/all/4CADAEEC020000780001B32C@vpn.id2.novell.com/ Although this issue does not seem to be easily triggerable, it is a potential memory corruption bug that should be fixed. This patch resolves the issue by ensuring the function returns the appropriate size for all three cases and validates that *max_len is large enough before writing any data.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Nov 12, 2025
Updated
Oct 19, 2026
EPSS
0.1% · 4th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-40205

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.29affected
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before 60de2f55d2aca53e81b4ef2a67d7cc9e1eb677dbaffected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before 742b44342204e5dfe3926433823623c1a0c581dfaffected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before d3a9a8e1275eb9b87f006b5562a287aea3f6885faffected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before d91f6626133698362bba08fbc04bd72c466806d3affected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before 0276c8582488022f057b4cec21975a5edf079f47affected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before 361d67276eb8ec6be8f27f4ad6c6090459438feeaffected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before 43143776b0a7604d873d1a6f3e552a00aa930224affected · git
    • be6e8dc0ba84029997075a1ec77b4ddb863cbe15 and later · before dff4f9ff5d7f289e4545cc936362e01ed3252742affected · git
    • before 2.6.29not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.158-16.1.158-1
Debian:13linuxbefore 6.12.57-16.12.57-1
Debian:14linuxbefore 6.17.6-16.17.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2025-40203Nov 12, 2025 · listmount: don't call path_put() under namespace semaphore
    31Monitor
  • ← EarlierCVE-2025-40204Nov 12, 2025 · sctp: Fix MAC comparison to be constant-time
    32Monitor
  • Later →CVE-2025-40206Nov 12, 2025 · netfilter: nft_objref: validate objref and objrefmap expressions
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0276c8582488022f057b4cec21975a5edf079f47Vendor (CNA)
Linux Linux361d67276eb8ec6be8f27f4ad6c6090459438feeVendor (CNA)
Linux Linux43143776b0a7604d873d1a6f3e552a00aa930224Vendor (CNA)
Linux Linux60de2f55d2aca53e81b4ef2a67d7cc9e1eb677dbVendor (CNA)
Linux Linux742b44342204e5dfe3926433823623c1a0c581dfVendor (CNA)
Linux Linuxd3a9a8e1275eb9b87f006b5562a287aea3f6885fVendor (CNA)
Linux Linuxd91f6626133698362bba08fbc04bd72c466806d3Vendor (CNA)
Linux Linuxdff4f9ff5d7f289e4545cc936362e01ed3252742Vendor (CNA)
azl3 kernel 6.6.112.1-2 on Azure Linux 3.06.6.117.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.158-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records