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7.8
Linux Kernel: IPv6 Fragmentation Data Corruption
published 4 months ago
Summary
A vulnerability in the Linux kernel's IPv6 fragmentation handling could allow an attacker to corrupt data by sending specially crafted UDPv6 packets. This could potentially lead to system instability or crashes. To mitigate this issue, update your Linux kernel to the latest version.
What to do
- Update linux kernel to version 7.1.3.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Linux | linux | kernel |
>= 6.19.0, < 7.1.3 Fix: upgrade to 7.1.3
|
Original advisory text
ipv6: account for fraggap on the paged allocation path
In the Linux kernel, the following vulnerability has been resolved:
ipv6: account for fraggap on the paged allocation path
In __ip6_append_data(), when the paged-allocation branch is taken
(MSG_MORE / NETIF_F_SG / large fraglen), alloclen and pagedlen are
computed as
alloclen = fragheaderlen + transhdrlen;
pagedlen = datalen - transhdrlen;
datalen already includes fraggap (datalen = length + fraggap). When
fraggap is non-zero, this is not the first skb and transhdrlen is zero.
The fraggap bytes carried over from the previous skb are copied just past
the fragment headers in the new skb's linear area. The linear area is
therefore undersized by fraggap bytes while pagedlen is overstated by the
same amount, and the copy writes past skb->end into the trailing
skb_shared_info.
An unprivileged user can trigger this via a UDPv6 socket using
MSG_MORE together with MSG_SPLICE_PAGES.
The bad accounting was introduced by commit 773ba4fe9104 ("ipv6:
avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix
__ip6_append_data()'s handling of MSG_SPLICE_PAGES"), the negative
copy value caused -EINVAL to be returned. That later commit allowed
MSG_SPLICE_PAGES to proceed in this case, making the corruption
triggerable.
The non-paged branch sets alloclen to fraglen, which already accounts
for fraggap because datalen does. Bring the paged branch in line by
adding fraggap to alloclen and subtracting it from pagedlen.
After this adjustment, copy no longer collapses to -fraggap on the
paged path, so remove the stale comment describing that old arithmetic.
Since a negative copy is no longer expected for a valid MSG_SPLICE_PAGES
case, remove the MSG_SPLICE_PAGES exception from the negative copy check.
ipv6: account for fraggap on the paged allocation path
In __ip6_append_data(), when the paged-allocation branch is taken
(MSG_MORE / NETIF_F_SG / large fraglen), alloclen and pagedlen are
computed as
alloclen = fragheaderlen + transhdrlen;
pagedlen = datalen - transhdrlen;
datalen already includes fraggap (datalen = length + fraggap). When
fraggap is non-zero, this is not the first skb and transhdrlen is zero.
The fraggap bytes carried over from the previous skb are copied just past
the fragment headers in the new skb's linear area. The linear area is
therefore undersized by fraggap bytes while pagedlen is overstated by the
same amount, and the copy writes past skb->end into the trailing
skb_shared_info.
An unprivileged user can trigger this via a UDPv6 socket using
MSG_MORE together with MSG_SPLICE_PAGES.
The bad accounting was introduced by commit 773ba4fe9104 ("ipv6:
avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix
__ip6_append_data()'s handling of MSG_SPLICE_PAGES"), the negative
copy value caused -EINVAL to be returned. That later commit allowed
MSG_SPLICE_PAGES to proceed in this case, making the corruption
triggerable.
The non-paged branch sets alloclen to fraglen, which already accounts
for fraggap because datalen does. Bring the paged branch in line by
adding fraggap to alloclen and subtracting it from pagedlen.
After this adjustment, copy no longer collapses to -fraggap on the
paged path, so remove the stale comment describing that old arithmetic.
Since a negative copy is no longer expected for a valid MSG_SPLICE_PAGES
case, remove the MSG_SPLICE_PAGES exception from the negative copy check.
References
- https://git.kernel.org/stable/c/14200d435af9a9eeb444f529fc2f689a236b7962 URL
- https://git.kernel.org/stable/c/46f201f8b4c39633a1fa3dc12459f506d470993d URL
- https://git.kernel.org/stable/c/6374fb9edf72c67a118a2c214a0dddd04c921e0a URL
- https://git.kernel.org/stable/c/65fb14cbebb0cd0eff903a22d33537ddc8b95769 URL
- https://git.kernel.org/stable/c/736b380e28d0480c7bc3e022f1950f31fe53a7c5 URL
- https://git.kernel.org/stable/c/e9eacf19281ea2498b36291b56c9606118c2d74e URL
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53362... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-53362 Vendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git Product
Internet-facing
14 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit (estimated)
- Gives an attacker full control (estimated)
Timeline
Published4 Jul 2026
Updated22 Jul 2026
First seen22 Jul 2026
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