Get an e-mail when this CVE is exploited, patched or re-scored. Free account.
Alert meAnalysisCVE.org
In the Linux kernel, the following vulnerability has been resolved:
net: ipv6: Fix UDP length overflow with PMTU discover and big MTU
This commit bounds cork->base.fragsize to IP6_MAX_MTU for UDP sockets to avoid a possible overflow of UDP length that triggers a WARN in udp_set_len_short when setsockopt IPV6_MTU_DISCOVER is set to IPV6_PMTUDISC_DO or IPV6_PMTUDISC_PROBE, and a large packet is sent over a netdev with an unusually large MTU.
Steps to reproduce (included in the new selftest):
- Set device MTU bigger than IP6_MAX_MTU. cork->base.fragsize will be
set to that MTU in ip6_setup_cork.
- Set IPV6_MTU_DISCOVER to IPV6_PMTUDISC_PROBE or IPV6_PMTUDISC_DO. It
lets maxnonfragsize be set to device MTU (cork->fragsize) in __ip6_append_data, rather than to IP6_MAX_MTU.
- Send 65528 bytes of payload (+8 bytes of UDP header, +40 bytes of
IPv6 header). Device MTU allows it (it's only one byte bigger than IP6_MAX_MTU, and the device MTU is bigger than that).
- The UDP length in the built packet is 65536, which overflows the
16-bit length field and triggers the WARN in udp_set_len_short.
To avoid breaking sending UDP jumbograms over raw IPv6 sockets, limit the change to UDP sockets only.
The original overflow bug with IPv6 and IPV6_PMTUDISC_DO seems to predate git history (verified reproduction on 2.6.21), was fixed later, and then reappeared in commit 427faee167bc ("net: ipv6: introduce ip6_dst_mtu_maybe_forward"), which is chosen as the Fixes tag here. The overflow with IPV6_PMTUDISC_PROBE reproduces since its introduction in commit 628a5c561890 ("[INET]: Add IP(V6)_PMTUDISC_RPOBE").
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Know when the next one hits your stack
- Watch products and get an email when something new is published
- Check this CVE against your own stack and servers
- Exploit and PoC references, threat intelligence from 22 sources
No credit card · 7-day full trial
Lifecycle Timeline
2Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
EUVD-2026-86638
GHSA-5m3w-7wwr-wqm2
CVE.org
EPSS
Exploit-DB