Linux Kernel up to 6.19.10 udp_lib_lport_inuse privilege escalation

CVSS Meta Temp Score
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CTI Interest Score
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5.3$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 6.1.167/6.6.130/6.12.79/6.18.20/6.19.10. The affected element is the function udp_lib_lport_inuse. Performing a manipulation results in an unknown weakness. This vulnerability is reported as CVE-2026-31503. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Linux Kernel up to 6.1.167/6.6.130/6.12.79/6.18.20/6.19.10. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: udp: Fix wildcard bind conflict check when using hash2 When binding a udp_sock to a local address and port, UDP uses two hashes (udptable->hash and udptable->hash2) for collision detection. The current code switches to "hash2" when hslot->count > 10. "hash2" is keyed by local address and local port. "hash" is keyed by local port only. The issue can be shown in the following bind sequence (pseudo code): bind(fd1, "[fd00::1]:8888") bind(fd2, "[fd00::2]:8888") bind(fd3, "[fd00::3]:8888") bind(fd4, "[fd00::4]:8888") bind(fd5, "[fd00::5]:8888") bind(fd6, "[fd00::6]:8888") bind(fd7, "[fd00::7]:8888") bind(fd8, "[fd00::8]:8888") bind(fd9, "[fd00::9]:8888") bind(fd10, "[fd00::10]:8888") /* Correctly return -EADDRINUSE because "hash" is used * instead of "hash2". udp_lib_lport_inuse() detects the * conflict. */ bind(fail_fd, "[::]:8888") /* After one more socket is bound to "[fd00::11]:8888", * hslot->count exceeds 10 and "hash2" is used instead. */ bind(fd11, "[fd00::11]:8888") bind(fail_fd, "[::]:8888") /* succeeds unexpectedly */ The same issue applies to the IPv4 wildcard address "0.0.0.0" and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For example, if there are existing sockets bound to "192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or "[::ffff:0.0.0.0]:8888" can also miss the conflict when hslot->count > 10. TCP inet_csk_get_port() already has the correct check in inet_use_bhash2_on_bind(). Rename it to inet_use_hash2_on_bind() and move it to inet_hashtables.h so udp.c can reuse it in this fix.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-31503 since 03/09/2026. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/18/2026).

The vulnerability scanner Nessus provides a plugin with the ID 313522 (Amazon Linux 2023 : bpftool, kernel, kernel-devel (ALAS2023-2026-1681)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.168, 6.6.131, 6.12.80, 6.18.21 or 6.19.11 eliminates this vulnerability. Applying the patch d6ace0dbcbb7fd285738bb87b42b71b01858c952/2297e38114316b26ae02f2d205c49b5511c5ed55/f1bed05a832ae79be5f7a105da56810eaa59a5f1/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4/0a360f7f73a06ac88f18917055fbcc79694252d7/e537dd15d0d4ad989d56a1021290f0c674dd8b28 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (313522) and CERT Bund (WID-SEC-2026-1252). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.3

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 313522
Nessus Name: Amazon Linux 2023 : bpftool, kernel, kernel-devel (ALAS2023-2026-1681)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.168/6.6.131/6.12.80/6.18.21/6.19.11
Patch: d6ace0dbcbb7fd285738bb87b42b71b01858c952/2297e38114316b26ae02f2d205c49b5511c5ed55/f1bed05a832ae79be5f7a105da56810eaa59a5f1/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4/0a360f7f73a06ac88f18917055fbcc79694252d7/e537dd15d0d4ad989d56a1021290f0c674dd8b28

Timelineinfo

03/09/2026 CVE reserved
04/22/2026 +43 days Advisory disclosed
04/22/2026 +0 days VulDB entry created
06/18/2026 +57 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-31503 (🔒)
GCVE (CVE): GCVE-0-2026-31503
GCVE (VulDB): GCVE-100-358947
CERT Bund: WID-SEC-2026-1252 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 04/22/2026 17:23
Updated: 06/18/2026 06:09
Changes: 04/22/2026 17:23 (56), 05/10/2026 10:48 (2), 06/18/2026 06:09 (7)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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