# [CRIT] One-Character Linux Kernel Flaw Enables Local Root Access, Exploits Now Public

**Source:** The Hacker News
**Published:** 2026-06-08
**Article:** https://thehackernews.com/2026/06/one-character-linux-kernel-flaw-enables.html

## Threat Profile

One-Character Linux Kernel Flaw Enables Local Root Access, Exploits Now Public 
 Swati Khandelwal  Jun 08, 2026 Linux / Vulnerability 
Security researchers have published a detailed, working exploit for a Linux kernel use-after-free that lets an unprivileged local user escalate to root and break out of a container.
The flaw, CVE-2026-23111, sits in the kernel's nf_tables packet-filtering code and was patched upstream on February 5, 2026. Exodus Intelligence released its full technical walkthro…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2026-23111`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1566.002** — Spearphishing Link
- **T1204.001** — User Execution: Malicious Link
- **T1059.001** — PowerShell
- **T1566.001** — Spearphishing Attachment
- **T1204.002** — User Execution: Malicious File
- **T1059.005** — Visual Basic
- **T1218** — System Binary Proxy Execution
- **T1528** — Steal Application Access Token
- **T1098.001** — Account Manipulation: Additional Cloud Credentials
- **T1195.002** — Compromise Software Supply Chain
- **T1068** — Exploitation for Privilege Escalation
- **T1611** — Escape to Host
- **T1562.004** — Impair Defenses: Disable or Modify System Firewall
- **T1588.006** — Obtain Capabilities: Vulnerabilities

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Unprivileged user namespace + nf_tables manipulation chain (CVE-2026-23111 exploitation)

`UC_100_7` · phase: **exploit** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=true count min(_time) as firstTime max(_time) as lastTime values(Processes.process) as cmds from datamodel=Endpoint.Processes where Processes.process_name IN ("unshare","nft") AND Processes.user!="root" AND Processes.user!="0" by Processes.dest Processes.user Processes.process_name _time span=10m
| `drop_dm_object_name(Processes)`
| eval is_unshare=if(process_name="unshare" AND match(cmds,"(?i)(\s|^)(-U|--user|-rU|-Ur|-Urm)(\s|$)"),1,0)
| eval is_nft=if(process_name="nft",1,0)
| stats sum(is_unshare) as unshare_cnt sum(is_nft) as nft_cnt values(cmds) as commands min(firstTime) as firstTime max(lastTime) as lastTime by dest user
| where unshare_cnt>=1 AND nft_cnt>=1
| convert ctime(firstTime) ctime(lastTime)
| sort - lastTime
```

**Defender KQL:**
```kql
let LookbackDays = 7d;
let WindowMinutes = 10m;
let NsCreate = DeviceProcessEvents
    | where Timestamp > ago(LookbackDays)
    | where FileName =~ "unshare" or FolderPath endswith "/unshare"
    | where ProcessCommandLine matches regex @"(?i)(\s|^)-(U|rU|Ur|Urm|-user)(\s|$)"
    | where AccountName != "root" and isnotempty(AccountName)
    | project NsTime = Timestamp, DeviceId, DeviceName, AccountName, NsCmd = ProcessCommandLine, NsParent = InitiatingProcessFileName;
let NftRun = DeviceProcessEvents
    | where Timestamp > ago(LookbackDays)
    | where FileName =~ "nft" or FolderPath endswith "/nft"
    | project NftTime = Timestamp, DeviceId, DeviceName, AccountName, NftCmd = ProcessCommandLine;
NsCreate
| join kind=inner NftRun on DeviceId, AccountName
| where NftTime between (NsTime .. NsTime + WindowMinutes)
| extend DelaySec = datetime_diff('second', NftTime, NsTime)
| project NsTime, NftTime, DelaySec, DeviceName, AccountName, NsCmd, NftCmd, NsParent
| order by NsTime desc
```

### nft (nftables) ruleset manipulation by non-root account on Linux endpoints

`UC_100_8` · phase: **exploit** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=true count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name="nft" AND (Processes.process="*add table*" OR Processes.process="*create table*" OR Processes.process="*add chain*" OR Processes.process="*create chain*" OR Processes.process="*add set*" OR Processes.process="*add map*" OR Processes.process="*add rule*") AND Processes.user!="root" AND Processes.user!="0" by Processes.dest Processes.user Processes.process Processes.parent_process_name Processes.parent_process
| `drop_dm_object_name(Processes)`
| convert ctime(firstTime) ctime(lastTime)
| sort - lastTime
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where FileName =~ "nft" or FolderPath endswith "/nft"
| where ProcessCommandLine has_any ("add table", "create table", "add chain", "create chain", "add set", "add map", "add rule")
| where AccountName != "root" and isnotempty(AccountName)
| where AccountSid != "S-1-5-18"
| project Timestamp, DeviceName, AccountName, FolderPath, ProcessCommandLine, InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessParentFileName
| order by Timestamp desc
```

### Linux assets carrying vulnerable kernel for CVE-2026-23111 (nf_tables UAF)

`UC_100_9` · phase: **recon** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=true count from datamodel=Vulnerabilities.Vulnerabilities where Vulnerabilities.cve="CVE-2026-23111" by Vulnerabilities.dest Vulnerabilities.signature Vulnerabilities.severity Vulnerabilities.os _time
| `drop_dm_object_name(Vulnerabilities)`
| sort - _time
```

**Defender KQL:**
```kql
DeviceTvmSoftwareVulnerabilities
| where CveId == "CVE-2026-23111"
| where OSPlatform has_any ("Linux", "Ubuntu", "Debian", "RHEL", "Red Hat", "CentOS", "Amazon", "SUSE")
| join kind=leftouter (DeviceInfo | summarize arg_max(Timestamp, *) by DeviceId) on DeviceId
| project Timestamp, DeviceName, OSPlatform, OSVersion, SoftwareName, SoftwareVersion, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, IsInternetFacing, PublicIP
| order by IsInternetFacing desc, Timestamp desc
```

### Phishing-link click correlated to endpoint execution

`UC_PHISH_LINK` · phase: **delivery** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Phishing-link click that drives endpoint execution within 60s ```
| tstats `summariesonly` earliest(_time) AS click_time
    from datamodel=Web
    where Web.action="allowed"
    by Web.src, Web.user, Web.dest, Web.url
| `drop_dm_object_name(Web)`
| rename user AS recipient, dest AS clicked_domain, url AS clicked_url
| join type=inner recipient
    [| tstats `summariesonly` count
         from datamodel=Email.All_Email
         where All_Email.action="delivered" AND All_Email.url!="-"
         by All_Email.recipient, All_Email.src_user, All_Email.url, All_Email.subject
     | `drop_dm_object_name(All_Email)`
     | rex field=url "https?://(?<email_domain>[^/]+)"
     | rename recipient AS recipient]
| join type=inner src
    [| tstats `summariesonly` earliest(_time) AS exec_time
         values(Processes.process) AS exec_cmd, values(Processes.process_name) AS exec_proc
         from datamodel=Endpoint.Processes
         where Processes.parent_process_name IN ("chrome.exe","msedge.exe","firefox.exe",
                                                   "outlook.exe","brave.exe","arc.exe")
           AND Processes.process_name IN ("powershell.exe","pwsh.exe","cmd.exe","mshta.exe",
                                            "rundll32.exe","regsvr32.exe","wscript.exe",
                                            "cscript.exe","bitsadmin.exe","certutil.exe",
                                            "curl.exe","wget.exe")
         by Processes.dest, Processes.user
     | `drop_dm_object_name(Processes)`
     | rename dest AS src]
| eval delta_sec = exec_time - click_time
| where delta_sec >= 0 AND delta_sec <= 60
| table click_time, exec_time, delta_sec, recipient, src, src_user, subject,
        clicked_domain, clicked_url, exec_proc, exec_cmd
| sort - click_time
```

**Defender KQL:**
```kql
// Phishing-link click that drives endpoint execution within 60s.
// Far higher fidelity than "every clicked URL" — most legitimate clicks
// never spawn a non-browser child process, so the join eliminates the
// 99% of noise that makes a raw click query unactionable.
let LookbackDays = 7d;
let SuspectClicks = UrlClickEvents
    | where Timestamp > ago(LookbackDays)
    | where AccountName !endswith "$"
    | where ActionType in ("ClickAllowed","ClickedThrough")
    | join kind=inner (
        EmailEvents
        | where Timestamp > ago(LookbackDays)
        | where DeliveryAction == "Delivered"
        | where EmailDirection == "Inbound"
        | project NetworkMessageId, Subject, SenderFromAddress, SenderFromDomain,
                  RecipientEmailAddress, EmailTimestamp = Timestamp
      ) on NetworkMessageId
    | join kind=leftouter (
        EmailUrlInfo | project NetworkMessageId, Url, UrlDomain
      ) on NetworkMessageId, Url
    | project ClickTime = Timestamp, AccountUpn, IPAddress, Url, UrlDomain,
              Subject, SenderFromAddress, SenderFromDomain, RecipientEmailAddress,
              ActionType;
// Correlate to a non-browser child process spawned within 60 seconds on
// the recipient's device.
DeviceProcessEvents
| where Timestamp > ago(LookbackDays)
| where InitiatingProcessFileName in~ ("chrome.exe","msedge.exe","firefox.exe",
                                         "outlook.exe","brave.exe","arc.exe")
| where FileName in~ ("powershell.exe","pwsh.exe","cmd.exe","mshta.exe",
                        "rundll32.exe","regsvr32.exe","wscript.exe","cscript.exe",
                        "bitsadmin.exe","certutil.exe","curl.exe","wget.exe")
| join kind=inner SuspectClicks on $left.AccountName == $right.AccountUpn
| where Timestamp between (ClickTime .. ClickTime + 60s)
| project ClickTime, ProcessTime = Timestamp,
          DelaySec = datetime_diff('second', Timestamp, ClickTime),
          DeviceName, AccountName, RecipientEmailAddress, SenderFromAddress,
          Subject, Url, UrlDomain, ActionType,
          FileName, ProcessCommandLine, InitiatingProcessFileName
| order by ClickTime desc
```

### Email attachment opened from external sender

`UC_PHISH_ATTACH` · phase: **delivery** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count
    from datamodel=Email.All_Email
    where All_Email.file_name!="-"
    by All_Email.src_user, All_Email.recipient, All_Email.file_name, All_Email.subject
| rename All_Email.recipient as user
| join type=inner user
    [| tstats `summariesonly` count
        from datamodel=Endpoint.Processes
        where Processes.parent_process_name IN ("OUTLOOK.EXE","winword.exe","excel.exe","powerpnt.exe")
          AND Processes.process_name IN ("cmd.exe","powershell.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe","regsvr32.exe")
        by Processes.dest, Processes.user, Processes.parent_process_name, Processes.process_name, Processes.process
     | rename Processes.user as user]
```

**Defender KQL:**
```kql
let LookbackDays = 7d;
let MalAttachments = EmailAttachmentInfo
    | where Timestamp > ago(LookbackDays)
    | where AccountName !endswith "$"
    | project NetworkMessageId, RecipientEmailAddress,
              AttachmentFileName = FileName, AttachmentSHA256 = SHA256;
DeviceProcessEvents
| where Timestamp > ago(LookbackDays)
| where InitiatingProcessFileName in~ ("OUTLOOK.EXE","winword.exe","excel.exe","powerpnt.exe")
| where FileName in~ ("cmd.exe","powershell.exe","wscript.exe","cscript.exe",
                      "mshta.exe","rundll32.exe","regsvr32.exe")
| join kind=inner MalAttachments on $left.AccountUpn == $right.RecipientEmailAddress
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine,
          InitiatingProcessFileName, AttachmentFileName, AttachmentSHA256
```

### Office app spawning script/LOLBin child process

`UC_OFFICE_CHILD` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.parent_process_name IN ("winword.exe","excel.exe","powerpnt.exe","outlook.exe","onenote.exe","mspub.exe","visio.exe")
      AND Processes.process_name IN ("cmd.exe","powershell.exe","pwsh.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe","regsvr32.exe","wmic.exe","bitsadmin.exe","certutil.exe")
    by Processes.dest, Processes.user, Processes.parent_process_name, Processes.process_name, Processes.process
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where InitiatingProcessFileName in~ ("winword.exe","excel.exe","powerpnt.exe","outlook.exe","onenote.exe","mspub.exe","visio.exe")
| where FileName in~ ("cmd.exe","powershell.exe","pwsh.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe","regsvr32.exe","wmic.exe","bitsadmin.exe","certutil.exe")
| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, FileName, ProcessCommandLine
```

### OAuth consent / suspicious app grant

`UC_OAUTH_ABUSE` · phase: **actions** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Authentication.Authentication
    where Authentication.action="success"
      AND Authentication.signature IN (
        "Consent to application",
        "Add app role assignment grant to user",
        "Add OAuth2PermissionGrant",
        "Add delegated permission grant")
    by Authentication.user, Authentication.app, Authentication.src, Authentication.signature
| `drop_dm_object_name(Authentication)`
```

**Defender KQL:**
```kql
CloudAppEvents
| where Timestamp > ago(7d)
| where ActionType in ("Consent to application.","Add OAuth2PermissionGrant.","Add delegated permission grant.")
| project Timestamp, AccountObjectId, AccountDisplayName, ActivityType,
          ActivityObjects, IPAddress, UserAgent
```

### Trusted vendor binary / installer launching unusual children

`UC_SUPPLY_CHAIN` · phase: **exploit** · confidence: **Medium**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.parent_process_name IN ("setup.exe","installer.exe","update.exe")
      AND Processes.process_name IN ("powershell.exe","cmd.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","cscript.exe","wmic.exe","bitsadmin.exe")
    by Processes.dest, Processes.user, Processes.parent_process_name, Processes.process_name, Processes.process
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where InitiatingProcessFileName in~ ("setup.exe","installer.exe","update.exe")
| where FileName in~ ("powershell.exe","cmd.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","cscript.exe","wmic.exe","bitsadmin.exe")
| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, FileName, ProcessCommandLine
```

### Article-specific behavioural hunt — One-Character Linux Kernel Flaw Enables Local Root Access, Exploits Now Public

`UC_100_6` · phase: **install** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — One-Character Linux Kernel Flaw Enables Local Root Access, Exploits Now Public ```
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_path="*/etc/shadow*")
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — One-Character Linux Kernel Flaw Enables Local Root Access, Exploits Now Public
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FolderPath has_any ("/etc/shadow"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2026-23111`


## Why this matters

Severity classified as **CRIT** based on: CVE present, 10 use case(s) fired, 15 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.