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9.8

Linux kernel can crash during IP payload compression

CVE-2026-63825 · published 2 months ago
Summary

The Linux kernel may stop working when multiple processors handle compressed network data at the same time. This happens because a shared counter used by a testing tool can be changed by one processor while another is reading it, leading to memory errors. Updating the kernel build settings to use atomic (indivisible) updates fixes the problem, so apply the provided patch or update to a version that includes it.

What to do
  • Update linux kernel to version 7.1.3.
  • Update debian rootio-linux to version 6.1.177-1.root.io.161.
  • Update debian linux to version 7.1.3-1.
  • Update debian rootio-linux to version 5.10.259-1.root.io.112.
  • Update debian rootio-linux to version 6.12.100-1.aikido.155.
  • Update canonical linux-aws-7.0 to version 7.0.0-1012.12~24.04.1.
  • Update canonical linux-azure-7.0 to version 7.0.0-1014.14~24.04.1.
  • Update canonical linux-gcp-7.0 to version 7.0.0-1011.11~24.04.1.
  • Update canonical linux-hwe-7.0 to version 7.0.0-31.31~24.04.1.
  • Update canonical linux-nvidia-7.0 to version 7.0.0-1018.18~24.04.1.
  • Update canonical linux-nvidia-tegra to version 6.8.0-1035.38.
  • Update canonical linux-riscv-7.0 to version 7.0.0-31.31.1~24.04.1.
  • Update canonical linux to version 7.0.0-31.31.
  • Update canonical linux-aws to version 7.0.0-1012.12.
  • Update canonical linux-azure to version 7.0.0-1014.14.
  • Update canonical linux-gcp to version 7.0.0-1011.11.
  • Update canonical linux-gke to version 7.0.0-1006.7.
  • Update canonical linux-ibm to version 7.0.0-1013.13.
  • Update canonical linux-nvidia to version 7.0.0-1018.18.
  • Update canonical linux-nvidia-bos to version 7.0.0-2018.18.
  • Update canonical linux-oem-7.0 to version 7.0.0-1013.13.
  • Update canonical linux-oracle to version 7.0.0-1011.11.
  • Update canonical linux-raspi to version 7.0.0-1019.19.
  • Update canonical linux-realtime to version 7.0.0-31.31.1.
  • Update canonical linux-riscv to version 7.0.0-31.31.1.
  • Update canonical linux-oracle-7.0 to version 7.0.0-1011.11~24.04.1.
  • Update linux to version 5.15.0-198.208.aikido.116.
  • Update rootio-linux to version 5.15.0-198.208.aikido.116.
  • Update linux linux to version 49d893b9cbcfc5802a32e53a64c6c6956670d65b or later.
Affected software
Ecosystem VendorProductAffected versions
Linux linux kernel >= 6.19.0, < 7.1.3
Fix: upgrade to 7.1.3
– linux linux < 49d893b9cbcfc5802a32e53a64c6c6956670d65b
2.6.31
Root:Debian:12 debian rootio-linux < 6.1.177-1.root.io.161
Fix: upgrade to 6.1.177-1.root.io.161
Ubuntu:Pro:14.04:LTS canonical linux All versions
Ubuntu:Pro:14.04:LTS canonical linux-aws All versions
Ubuntu:Pro:14.04:LTS canonical linux-azure All versions
Ubuntu:Pro:14.04:LTS canonical linux-lts-xenial All versions
Ubuntu:Pro:16.04:LTS canonical linux-aws-hwe All versions
Ubuntu:Pro:16.04:LTS canonical linux-gcp All versions
Ubuntu:Pro:16.04:LTS canonical linux-hwe All versions
Ubuntu:16.04:LTS canonical linux-hwe-edge All versions
Ubuntu:Pro:16.04:LTS canonical linux-kvm All versions
Ubuntu:Pro:16.04:LTS canonical linux-oracle All versions
Ubuntu:Pro:FIPS:16.04:LTS canonical linux-fips All versions
Ubuntu:18.04:LTS canonical linux-aws-5.0 All versions
Ubuntu:18.04:LTS canonical linux-aws-5.3 All versions
Ubuntu:Pro:18.04:LTS canonical linux-aws-5.4 All versions
Ubuntu:Pro:18.04:LTS canonical linux-azure-4.15 All versions
Ubuntu:18.04:LTS canonical linux-azure-5.3 All versions
Ubuntu:Pro:18.04:LTS canonical linux-azure-5.4 All versions
Ubuntu:18.04:LTS canonical linux-azure-edge All versions
Ubuntu:Pro:18.04:LTS canonical linux-gcp-4.15 All versions
Ubuntu:18.04:LTS canonical linux-gcp-5.3 All versions
Ubuntu:Pro:18.04:LTS canonical linux-gcp-5.4 All versions
Ubuntu:18.04:LTS canonical linux-gke-4.15 All versions
Ubuntu:18.04:LTS canonical linux-gke-5.4 All versions
Ubuntu:18.04:LTS canonical linux-gkeop-5.4 All versions
Ubuntu:Pro:18.04:LTS canonical linux-hwe-5.4 All versions
Ubuntu:Pro:18.04:LTS canonical linux-ibm-5.4 All versions
Ubuntu:18.04:LTS canonical linux-oem All versions
Ubuntu:18.04:LTS canonical linux-oracle-5.0 All versions
Ubuntu:18.04:LTS canonical linux-oracle-5.3 All versions
Ubuntu:Pro:18.04:LTS canonical linux-oracle-5.4 All versions
Ubuntu:Pro:18.04:LTS canonical linux-raspi-5.4 All versions
Ubuntu:Pro:FIPS-updates:18.04:LTS canonical linux-aws-fips All versions
Ubuntu:Pro:FIPS-updates:18.04:LTS canonical linux-azure-fips All versions
Ubuntu:Pro:FIPS-updates:18.04:LTS canonical linux-gcp-fips All versions
Ubuntu:20.04:LTS canonical linux-aws-5.11 All versions
Ubuntu:20.04:LTS canonical linux-aws-5.13 All versions
Ubuntu:Pro:20.04:LTS canonical linux-aws-5.15 All versions
Ubuntu:20.04:LTS canonical linux-aws-5.8 All versions
Ubuntu:20.04:LTS canonical linux-azure-5.11 All versions
Ubuntu:20.04:LTS canonical linux-azure-5.13 All versions
Ubuntu:Pro:20.04:LTS canonical linux-azure-5.15 All versions
Ubuntu:20.04:LTS canonical linux-azure-5.8 All versions
Ubuntu:20.04:LTS canonical linux-azure-fde All versions
Ubuntu:Pro:20.04:LTS canonical linux-azure-fde-5.15 All versions
Ubuntu:Pro:20.04:LTS canonical linux-bluefield All versions
Ubuntu:20.04:LTS canonical linux-gcp-5.11 All versions
Ubuntu:20.04:LTS canonical linux-gcp-5.13 All versions
Showing 50 of 192. Show the rest
Ecosystem VendorProductAffected versions
Ubuntu:Pro:20.04:LTS canonical linux-gcp-5.15 All versions
Ubuntu:20.04:LTS canonical linux-gcp-5.8 All versions
Ubuntu:20.04:LTS canonical linux-gke All versions
Ubuntu:20.04:LTS canonical linux-gke-5.15 All versions
Ubuntu:20.04:LTS canonical linux-gkeop All versions
Ubuntu:20.04:LTS canonical linux-gkeop-5.15 All versions
Ubuntu:20.04:LTS canonical linux-hwe-5.11 All versions
Ubuntu:20.04:LTS canonical linux-hwe-5.13 All versions
Ubuntu:Pro:20.04:LTS canonical linux-hwe-5.15 All versions
Ubuntu:20.04:LTS canonical linux-hwe-5.8 All versions
Ubuntu:Pro:20.04:LTS canonical linux-ibm All versions
Ubuntu:Pro:20.04:LTS canonical linux-ibm-5.15 All versions
Ubuntu:20.04:LTS canonical linux-intel-5.13 All versions
Ubuntu:Pro:20.04:LTS canonical linux-intel-iotg-5.15 All versions
Ubuntu:Pro:20.04:LTS canonical linux-iot All versions
Ubuntu:Pro:20.04:LTS canonical linux-lowlatency-hwe-5.15 All versions
Ubuntu:Pro:20.04:LTS canonical linux-nvidia-tegra-5.15 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.10 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.13 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.14 All versions
Ubuntu:20.04:LTS canonical linux-oem-5.6 All versions
Ubuntu:20.04:LTS canonical linux-oracle-5.11 All versions
Ubuntu:20.04:LTS canonical linux-oracle-5.13 All versions
Ubuntu:Pro:20.04:LTS canonical linux-oracle-5.15 All versions
Ubuntu:20.04:LTS canonical linux-oracle-5.8 All versions
Ubuntu:Pro:20.04:LTS canonical linux-raspi All versions
Ubuntu:20.04:LTS canonical linux-raspi2 All versions
Ubuntu:20.04:LTS canonical linux-riscv All versions
Ubuntu:20.04:LTS canonical linux-riscv-5.11 All versions
Ubuntu:Pro:20.04:LTS canonical linux-riscv-5.15 All versions
Ubuntu:20.04:LTS canonical linux-riscv-5.8 All versions
Ubuntu:Pro:20.04:LTS canonical linux-xilinx-zynqmp All versions
Ubuntu:22.04:LTS canonical linux-allwinner-5.19 All versions
Ubuntu:22.04:LTS canonical linux-aws-5.19 All versions
Ubuntu:22.04:LTS canonical linux-aws-6.2 All versions
Ubuntu:22.04:LTS canonical linux-aws-6.5 All versions
Ubuntu:22.04:LTS canonical linux-aws-6.8 All versions
Ubuntu:22.04:LTS canonical linux-azure-5.19 All versions
Ubuntu:22.04:LTS canonical linux-azure-6.2 All versions
Ubuntu:22.04:LTS canonical linux-azure-6.5 All versions
Ubuntu:22.04:LTS canonical linux-azure-6.8 All versions
Ubuntu:22.04:LTS canonical linux-azure-fde-5.19 All versions
Ubuntu:22.04:LTS canonical linux-azure-fde-6.2 All versions
Ubuntu:22.04:LTS canonical linux-azure-fde-6.8 All versions
Ubuntu:22.04:LTS canonical linux-gcp-5.19 All versions
Ubuntu:22.04:LTS canonical linux-gcp-6.2 All versions
Ubuntu:22.04:LTS canonical linux-gcp-6.5 All versions
Ubuntu:22.04:LTS canonical linux-gcp-6.8 All versions
Ubuntu:22.04:LTS canonical linux-hwe-5.19 All versions
Ubuntu:22.04:LTS canonical linux-hwe-6.2 All versions
Ubuntu:22.04:LTS canonical linux-hwe-6.5 All versions
Ubuntu:22.04:LTS canonical linux-hwe-6.8 All versions
Ubuntu:22.04:LTS canonical linux-ibm-6.8 All versions
Ubuntu:22.04:LTS canonical linux-intel-iot-realtime All versions
Ubuntu:22.04:LTS canonical linux-intel-iotg All versions
Ubuntu:22.04:LTS canonical linux-lowlatency All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-5.19 All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-6.2 All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-6.5 All versions
Ubuntu:22.04:LTS canonical linux-lowlatency-hwe-6.8 All versions
Ubuntu:22.04:LTS canonical linux-nvidia All versions
Ubuntu:22.04:LTS canonical linux-nvidia-6.2 All versions
Ubuntu:22.04:LTS canonical linux-nvidia-6.5 All versions
Ubuntu:22.04:LTS canonical linux-nvidia-6.8 All versions
Ubuntu:22.04:LTS canonical linux-nvidia-tegra All versions
Ubuntu:22.04:LTS canonical linux-nvidia-tegra-igx All versions
Ubuntu:22.04:LTS canonical linux-oem-5.17 All versions
Ubuntu:22.04:LTS canonical linux-oem-6.0 All versions
Ubuntu:22.04:LTS canonical linux-oem-6.1 All versions
Ubuntu:22.04:LTS canonical linux-oem-6.5 All versions
Ubuntu:22.04:LTS canonical linux-oracle-6.5 All versions
Ubuntu:22.04:LTS canonical linux-oracle-6.8 All versions
Ubuntu:22.04:LTS canonical linux-realtime All versions
Ubuntu:22.04:LTS canonical linux-riscv-5.19 All versions
Ubuntu:22.04:LTS canonical linux-riscv-6.5 All versions
Ubuntu:22.04:LTS canonical linux-riscv-6.8 All versions
Ubuntu:22.04:LTS canonical linux-starfive-5.19 All versions
Ubuntu:22.04:LTS canonical linux-starfive-6.2 All versions
Ubuntu:22.04:LTS canonical linux-starfive-6.5 All versions
Ubuntu:Pro:Realtime:22.04:LTS canonical linux-realtime-6.8 All versions
Ubuntu:24.04:LTS canonical linux-aws-6.14 All versions
Ubuntu:24.04:LTS canonical linux-aws-6.17 All versions
Ubuntu:24.04:LTS canonical linux-aws-7.0 < 7.0.0-1012.12~24.04.1
Fix: upgrade to 7.0.0-1012.12~24.04.1
Ubuntu:24.04:LTS canonical linux-azure-6.11 All versions
Ubuntu:24.04:LTS canonical linux-azure-6.14 All versions
Ubuntu:24.04:LTS canonical linux-azure-6.17 All versions
Ubuntu:24.04:LTS canonical linux-azure-7.0 < 7.0.0-1014.14~24.04.1
Fix: upgrade to 7.0.0-1014.14~24.04.1
Ubuntu:24.04:LTS canonical linux-azure-fde-6.14 All versions
Ubuntu:24.04:LTS canonical linux-azure-fde-6.17 All versions
Ubuntu:24.04:LTS canonical linux-azure-fde-7.0 All versions
Ubuntu:24.04:LTS canonical linux-azure-nvidia All versions
Ubuntu:24.04:LTS canonical linux-azure-nvidia-6.14 All versions
Ubuntu:24.04:LTS canonical linux-gcp-6.11 All versions
Ubuntu:24.04:LTS canonical linux-gcp-6.14 All versions
Ubuntu:24.04:LTS canonical linux-gcp-6.17 All versions
Ubuntu:24.04:LTS canonical linux-gcp-7.0 < 7.0.0-1011.11~24.04.1
Fix: upgrade to 7.0.0-1011.11~24.04.1
Ubuntu:24.04:LTS canonical linux-hwe-6.11 All versions
Ubuntu:24.04:LTS canonical linux-hwe-6.14 All versions
Ubuntu:24.04:LTS canonical linux-hwe-6.17 All versions
Ubuntu:24.04:LTS canonical linux-hwe-7.0 < 7.0.0-31.31~24.04.1
Fix: upgrade to 7.0.0-31.31~24.04.1
Ubuntu:24.04:LTS canonical linux-lowlatency-hwe-6.11 All versions
Ubuntu:24.04:LTS canonical linux-nvidia-6.11 All versions
Ubuntu:24.04:LTS canonical linux-nvidia-6.17 All versions
Ubuntu:24.04:LTS canonical linux-nvidia-7.0 < 7.0.0-1018.18~24.04.1
Fix: upgrade to 7.0.0-1018.18~24.04.1
Ubuntu:24.04:LTS canonical linux-nvidia-lowlatency All versions
Ubuntu:24.04:LTS canonical linux-oem-6.11 All versions
Ubuntu:24.04:LTS canonical linux-oem-6.14 All versions
Ubuntu:24.04:LTS canonical linux-oem-6.17 All versions
Ubuntu:24.04:LTS canonical linux-oem-6.8 All versions
Ubuntu:24.04:LTS canonical linux-oracle-6.14 All versions
Ubuntu:24.04:LTS canonical linux-oracle-6.17 All versions
Ubuntu:24.04:LTS canonical linux-oracle-7.0 < 7.0.0-1011.11~24.04.1
Fix: upgrade to 7.0.0-1011.11~24.04.1
Ubuntu:24.04:LTS canonical linux-raspi-realtime All versions
Ubuntu:24.04:LTS canonical linux-riscv-6.14 All versions
Ubuntu:24.04:LTS canonical linux-riscv-6.17 All versions
Ubuntu:24.04:LTS canonical linux-riscv-7.0 < 7.0.0-31.31.1~24.04.1
Fix: upgrade to 7.0.0-31.31.1~24.04.1
Ubuntu:24.04:LTS canonical linux-xilinx All versions
Ubuntu:Pro:Realtime:24.04:LTS canonical linux-realtime-6.14 All versions
Ubuntu:Pro:Realtime:24.04:LTS canonical linux-realtime-6.17 All versions
Ubuntu:26.04:LTS canonical linux-nvidia-bos < 7.0.0-2018.18
Fix: upgrade to 7.0.0-2018.18
Ubuntu:26.04:LTS canonical linux-oem-7.0 < 7.0.0-1013.13
Fix: upgrade to 7.0.0-1013.13
Debian:11 debian linux All versions
Debian:12 debian linux All versions
Debian:13 debian linux All versions
Debian:14 debian linux < 7.1.3-1
Fix: upgrade to 7.1.3-1
Root:Debian:11 debian rootio-linux < 5.10.259-1.root.io.112
Fix: upgrade to 5.10.259-1.root.io.112
Root:Debian:13 debian rootio-linux < 6.12.100-1.aikido.155
Fix: upgrade to 6.12.100-1.aikido.155
Ubuntu:24.04:LTS canonical linux-nvidia-tegra < 6.8.0-1035.38
Fix: upgrade to 6.8.0-1035.38
Ubuntu:26.04:LTS canonical linux < 7.0.0-31.31
Fix: upgrade to 7.0.0-31.31
Ubuntu:26.04:LTS canonical linux-aws < 7.0.0-1012.12
Fix: upgrade to 7.0.0-1012.12
Ubuntu:26.04:LTS canonical linux-azure < 7.0.0-1014.14
Fix: upgrade to 7.0.0-1014.14
Ubuntu:26.04:LTS canonical linux-gcp < 7.0.0-1011.11
Fix: upgrade to 7.0.0-1011.11
Ubuntu:26.04:LTS canonical linux-gke < 7.0.0-1006.7
Fix: upgrade to 7.0.0-1006.7
Ubuntu:26.04:LTS canonical linux-ibm < 7.0.0-1013.13
Fix: upgrade to 7.0.0-1013.13
Ubuntu:26.04:LTS canonical linux-nvidia < 7.0.0-1018.18
Fix: upgrade to 7.0.0-1018.18
Ubuntu:26.04:LTS canonical linux-oracle < 7.0.0-1011.11
Fix: upgrade to 7.0.0-1011.11
Ubuntu:26.04:LTS canonical linux-raspi < 7.0.0-1019.19
Fix: upgrade to 7.0.0-1019.19
Ubuntu:26.04:LTS canonical linux-realtime < 7.0.0-31.31.1
Fix: upgrade to 7.0.0-31.31.1
Ubuntu:26.04:LTS canonical linux-riscv < 7.0.0-31.31.1
Fix: upgrade to 7.0.0-31.31.1
Root:Ubuntu:22.04 – linux < 5.15.0-198.208.aikido.116
Fix: upgrade to 5.15.0-198.208.aikido.116
Root:Ubuntu:22.04 – rootio-linux < 5.15.0-198.208.aikido.116
Fix: upgrade to 5.15.0-198.208.aikido.116
Ubuntu:24.04:LTS canonical linux-vmware All versions
Original advisory text
CVE-2026-63825 in linux - Patched by Root
In the Linux kernel, the following vulnerability has been resolved: gcov: use atomic counter updates to fix concurrent access crashes GCC's GCOV instrumentation can merge global branch counters with loop induction variables as an optimization. In inflate_fast(), the inner copy loops get transformed so that the GCOV counter value is loaded multiple times to compute the loop base address, start index, and end bound. Since GCOV counters are global (not per-CPU), concurrent execution on different CPUs causes the counter to change between loads, producing inconsistent values and out-of-bounds memory writes. The crash manifests during IPComp (IP Payload Compression) processing when inflate_fast() runs concurrently on multiple CPUs: BUG: unable to handle page fault for address: ffffd0a3c0902ffa RIP: inflate_fast+1431 Call Trace: zlib_inflate __deflate_decompress crypto_comp_decompress ipcomp_decompress [xfrm_ipcomp] ipcomp_input [xfrm_ipcomp] xfrm_input At the crash point, the compiler generated three loads from the same global GCOV counter (__gcov0.inflate_fast+216) to compute base, start, and end for an indexed loop. Another CPU modified the counter between loads, making the values inconsistent - the write went 3.4 MB past a 65 KB buffer. Add -fprofile-update=prefer-atomic to CFLAGS_GCOV at the global level in the top-level Makefile, guarded by a try-run compile test. The test compiles a minimal program with and without -fprofile-update=prefer-atomic using the full KBUILD_CFLAGS, then compares undefined symbols in the resulting object files. If prefer-atomic introduces new undefined references (such as __atomic_fetch_add_8 on i386 or __aarch64_ldadd8_relax on arm64 with outline-atomics), the flag is not added -- the kernel does not link against libatomic. On architectures where GCC inlines 64-bit atomic counter updates (x86_64, s390, ...) the test passes and the flag is enabled, preventing the compiler from merging counters with loop induction variables and fixing the observed concurrent-access crash. On architectures where the flag would introduce libatomic dependencies, it is silently omitted and behaviour is no worse than before this patch. Move the CFLAGS_GCOV block from its original position (before the arch Makefile include) to after the core KBUILD_CFLAGS assignments but before the scripts/Makefile.gcc-plugins include. This placement ensures the try-run test sees arch-specific flags (-m32, -march=, -mno-outline-atomics) while avoiding GCC plugin flags (-fplugin=) that would break the test on clean builds when plugin shared objects do not yet exist.
References
Fix within
Internet-facing 3 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically (estimated)
  • Gives an attacker full control (estimated)
Severity
9.8 Critical
Exploitation
<1% chance of attack within 30 days
Timeline
Published19 Jul 2026
Updated12 Oct 2026
First seen19 Jul 2026
Sources
ROOT-OS-DEBIAN-11-CVE-2026-63825 · OSV
ROOT-OS-DEBIAN-13-CVE-2026-63825 · OSV
CVE-2026-63825 · NVD
CVE-2026-63825 · MITRE
CVE-2026-63825 · OSV
DEBIAN-CVE-2026-63825 · OSV
ROOT-OS-DEBIAN-12-CVE-2026-63825 · OSV
UBUNTU-CVE-2026-63825 · OSV
ROOT-OS-UBUNTU-2204-CVE-2026-63825 · OSV
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