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CVE Record

CVE-2026-23331: udp: Unhash auto-bound connected sk from 4-tuple hash table when disconnected.

In the Linux kernel, the following vulnerability has been resolved: udp: Unhash auto-bound connected sk from 4-tuple hash table when disconnected. Let's say we bind() an UDP socket to the wildcard address with a non-zero port, connect() it to an address, and disconnect it from the address. bind() sets SOCK_BINDPORT_LOCK on sk->sk_userlocks (but not SOCK_BINDADDR_LOCK), and connect() calls udp_lib_hash4() to put the socket into the 4-tuple hash table. Then, __udp_disconnect() calls sk->sk_prot->rehash(sk). It computes a new hash based on the wildcard address and moves the socket to a new slot in the 4-tuple hash table, leaving a garbage in the chain that no packet hits. Let's remove such a socket from 4-tuple hash table when disconnected. Note that udp_sk(sk)->udp_portaddr_hash needs to be udpated after udp_hash4_dec(hslot2) in udp_unhash4().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2026-23331 is a Linux kernel UDP handling bug involving sockets that are bound, connected, then disconnected. The public record describes a correctness fix in kernel socket hashing, but does not state a concrete security impact, CVSS score, or active exploitation.

Executive priority

Treat as a tracking item until vendors clarify impact. Patch through normal kernel maintenance unless your Linux vendor rates it higher or affected systems are high-value UDP infrastructure.

Technical view

The issue occurs when a UDP socket bound to a wildcard address with a non-zero port is connected and later disconnected. The socket can be rehashed into the 4-tuple table incorrectly, leaving stale chain data unreachable by packets. The fix removes such sockets from the 4-tuple hash table on disconnect.

Likely exposure

Exposure is limited to systems running affected Linux kernel versions identified by the CVE record. The provided version data is incomplete and somewhat inconsistent, so confirm exposure through distribution advisories or kernel commit inclusion.

Exploitation context

No CISA KEV listing or cited source indicates active exploitation. The described trigger requires UDP socket lifecycle behavior by software on the system. The public sources do not define privilege requirements, impact severity, or remote exploitability.

Researcher notes

The record documents a kernel UDP hash-table cleanup defect, but omits CVSS, CWE, and security impact. Avoid assuming remote code execution or denial of service without additional vendor evidence. Version applicability should be validated against exact distro backports.

Mitigation direction

  • Check Linux distribution advisories for CVE-2026-23331 applicability.
  • Apply vendor kernel updates that include the referenced stable fixes.
  • If self-building kernels, verify inclusion of the listed upstream stable commits.
  • Prioritize systems with heavy UDP workloads after vendor confirmation.

Validation and detection

  • Inventory Linux kernel versions across servers and appliances.
  • Map installed kernels to vendor advisories for this CVE.
  • Check whether the referenced stable commits are present in custom kernels.
  • Monitor CVE and vendor pages for severity or impact updates.
Prepared
Confidence
medium
Sources
5

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2026-23331 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

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
LinuxLinux78c91ae2c6deb5d236a5a93ff2995cdd05514380, 78c91ae2c6deb5d236a5a93ff2995cdd05514380, 78c91ae2c6deb5d236a5a93ff2995cdd05514380unaffected
LinuxLinux6.13, 0, 6.18.17, 6.19.7, 7.0affected
Weakness

CWE details

No CWE listed

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