CVE-2026-64600
In the Linux kernel, the following vulnerability has been resolved: xfs: resample the data fork mapping after cycling ILOCK xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode, a data fork mapping, and a cow fork mapping. Unfortunately, these two helpers cycle the ILOCK to grab a transaction, which means that the mappings are stale as soon as we reacquire the ILOCK. Currently we refresh the cow fork mapping by re-calling xfs_find_trim_cow_extent, but we don't refresh the data fork mapping beforehand, which means that the xfs_bmap_trim_cow in that function queries the refcount btree about the wrong physical blocks and returns an inaccurate value in *shared. If *shared is now false, the directio write proceeds with a stale data fork mapping. Fix this by querying the data fork mapping if the sequence counter changes across the ILOCK cycle.
- CVSS
- 7.8Highscored by the publisher (CNA)
- Exploited in the wild
- Not knownUnvetted proof-of-concept code on GitHub; not in CISA KEV
- EPSS
- 0.47%chance of exploitation in the next 30 daystop 60% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Fixed in < 4.11, >= 5.15.212 and <= 5.15.*, >= 6.1.178 and <= 6.1.*per the vendor; 5 more listed below
- Published
- 23 Jul 2026analysed here 12 Nov 2026
Do first. Upgrade to a fixed release: < 4.11, >= 5.15.212 and <= 5.15.*, >= 6.1.178 and <= 6.1.*, >= 6.6.145 and <= 6.6.* (and 4 more below).
Summary
Triage
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Linux | >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < dc11be133efca5fe3a2fb02b016dee825cc12f18>= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < b8c9aa832b52680ee40d6cab0efb081f9a69df05>= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 50f0012da1040f69a4e788cd9aed587c9a04983f>= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < e705d81a7193dd19e69b8e2bad4696d78a4ea075>= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 206c09b04dc5469c7ff14d8aceff2d47c88078d9>= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 44f891bc088958399eec27f7604928694aa35581>= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 2f4acd0fcd862e22eab45690ec2c08c80b6ef2e74.11Vendor says fixed in: < 4.11, >= 5.15.212 and <= 5.15.*, >= 6.1.178 and <= 6.1.*, >= 6.6.145 and <= 6.6.*, >= 6.12.96 and <= 6.12.*, >= 6.18.39 and <= 6.18.*, >= 7.1.4 and <= 7.1.*, >= 7.2 and <= * |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- linux:linux_kernel
Fix and mitigation
WAF and other mitigations
Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.
Also consider: patch
Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Not listed as of our last sync.
- Public exploit code
- Unvetted proof-of-concept code on GitHub: 10 GitHub proofs of concept
- CISA SSVC
- exploitation none, automatable no, technical impact totalAssessed by CISA 16 Oct 2026 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
GitHub proofs of concept
- 0xBlackash/CVE-2026-6460022 stars
- Debajyoti0-0/CVE-2026-646007 stars
- litosmartin/CVE-2026-64600-Refluxfs-PoC4 stars
- masrikky/CVE-2026-64600-RefluXFS1 stars
and 6 more repositories
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 22 Jul 2026First proof-of-concept repository on GitHub (unvetted)
- 23 Jul 2026Published1 day later
- 16 Oct 2026CISA SSVC assessment: exploitation none85 days (about 3 months) later
- 19 Oct 2026CVE record last updated3 days later
- 12 Nov 2026Analysed by vulneraibility.com24 days later
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
| Metric | Value | What it means |
|---|---|---|
| Attack vector | LocalLocal access required (shell, logged-in user). | Local access required (shell, logged-in user). |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | LowThe attacker needs basic user privileges. | The attacker needs basic user privileges. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | HighComplete modification possible. | Complete modification possible. |
| Availability | HighFull outage possible. | Full outage possible. |
Common questions
Is CVE-2026-64600 being exploited?
Not confirmed. CVE-2026-64600 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.47% probability of exploitation in the next 30 days.
How severe is CVE-2026-64600?
CVE-2026-64600 is rated High with a CVSS score of 7.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-64600?
Yes. A fix has been recorded for CVE-2026-64600. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64600 affect?
CVE-2026-64600 affects linux:linux_kernel. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
14 references in the CVE record, grouped by the tags the record gives them.
Other links (14)
- git.kernel.org /stable/c/dc11be133efca5fe3a2fb02b016dee825cc12f18
- git.kernel.org /stable/c/b8c9aa832b52680ee40d6cab0efb081f9a69df05
- git.kernel.org /stable/c/50f0012da1040f69a4e788cd9aed587c9a04983f
- git.kernel.org /stable/c/e705d81a7193dd19e69b8e2bad4696d78a4ea075
- git.kernel.org /stable/c/206c09b04dc5469c7ff14d8aceff2d47c88078d9
- git.kernel.org /stable/c/44f891bc088958399eec27f7604928694aa35581
Show 8 more
- git.kernel.org /stable/c/2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7
- cdn2.qualys.com /advisory/2026/07/22/RefluXFS.txt
- openwall.com /lists/oss-security/2026/07/22/14
- openwall.com /lists/oss-security/2026/07/22/18
- openwall.com /lists/oss-security/2026/07/22/19
- openwall.com /lists/oss-security/2026/07/31/3
- openwall.com /lists/oss-security/2026/08/03/4
- openwall.com /lists/oss-security/2026/08/03/8
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
Similar CVEs
Get CVEs like this by email. Join the free digest: the CVEs we flag as major, all CVSS 8.0 or higher, in up to three emails a day (sent at 05:00, 11:00 and 15:00 UTC). Matching alerts to the products you run needs an account, and accounts are invite-only during the beta.