Linux · Kernel
CVE-2026-53362
ipv6: account for fraggap on the paged allocation path
What it is
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.
CISA: Linux Kernel contains an unspecified vulnerability that can allow for privilege escalation via IPv6 networking subsystem. This vulnerability can impact multiple products, including but not limited to Suse, Red Hat, and other products using Linux.
What to do
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Deadline for US federal agencies: August 30, 2026
- Added to the CISA list
- August 27, 2026
- Published
- July 4, 2026
- Severity
- High 7.8 CVSS 3.1
- Chance of attacks in the next 30 days (EPSS)
- 0.7% in the top 46.7% of all known vulnerabilities
- More details
- NVD · CVE.org · CISA
All references (6)
- https://git.kernel.org/stable/c/14200d435af9a9eeb444f529fc2f689a236b7962
- https://git.kernel.org/stable/c/65fb14cbebb0cd0eff903a22d33537ddc8b95769
- https://git.kernel.org/stable/c/46f201f8b4c39633a1fa3dc12459f506d470993d
- https://git.kernel.org/stable/c/6374fb9edf72c67a118a2c214a0dddd04c921e0a
- https://git.kernel.org/stable/c/e9eacf19281ea2498b36291b56c9606118c2d74e
- https://git.kernel.org/stable/c/736b380e28d0480c7bc3e022f1950f31fe53a7c5
More exploited flaws from Linux
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Sep 18, 2026 | Improper Check for Unusual or Exceptional Conditions | Kernel | Critical 9.8 | 3.3% |
| Sep 18, 2026 | Race Condition | Kernel | High 7.8 | 1.6% |
| Sep 18, 2026 | Out-of-Bounds Write | Kernel | High 8.8 | 0.9% |
| Aug 26, 2026 | Out-of-Bounds Write | Kernel | High 7.8 | 8.9% |
| Jun 2, 2026 | Improper Authentication | Kernel | High 7.8 | 5.5% |
| May 1, 2026 | Incorrect Resource Transfer Between Spheres | Kernel | High 7.8 | 98% |
| Jan 26, 2026 | Integer Overflow | Kernel | High 7.8 | 15% |
| Oct 6, 2025 | Heap Out-of-Bounds Write | Kernel | High 8.3 | 79% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.