CVE-2026-31503 (GCVE-0-2026-31503)
Vulnerability from cvelistv5 – Published: 2026-04-22 13:54 – Updated: 2026-04-22 13:54
VLAI?
Title
udp: Fix wildcard bind conflict check when using hash2
Summary
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux |
Affected:
30fff9231fad757c061285e347b33c5149c2c2e4 , < d6ace0dbcbb7fd285738bb87b42b71b01858c952
(git)
Affected: 30fff9231fad757c061285e347b33c5149c2c2e4 , < 2297e38114316b26ae02f2d205c49b5511c5ed55 (git) Affected: 30fff9231fad757c061285e347b33c5149c2c2e4 , < f1bed05a832ae79be5f7a105da56810eaa59a5f1 (git) Affected: 30fff9231fad757c061285e347b33c5149c2c2e4 , < 18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4 (git) Affected: 30fff9231fad757c061285e347b33c5149c2c2e4 , < 0a360f7f73a06ac88f18917055fbcc79694252d7 (git) Affected: 30fff9231fad757c061285e347b33c5149c2c2e4 , < e537dd15d0d4ad989d56a1021290f0c674dd8b28 (git) |
|||||||
|
|||||||||
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}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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