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Fencer Vulns
medium 5.5

CVE-2022-49520 json

arm64: compat: Do not treat syscall number as ESR_ELx for a bad syscall

published 2025-02-26 20 mo ago modified 2026-08-15 2 mo ago also EUVD-2022-54709

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

arm64: compat: Do not treat syscall number as ESR_ELx for a bad syscall

If a compat process tries to execute an unknown system call above the __ARM_NR_COMPAT_END number, the kernel sends a SIGILL signal to the offending process. Information about the error is printed to dmesg in compat_arm_syscall() -> arm64_notify_die() -> arm64_force_sig_fault() -> arm64_show_signal().

arm64_show_signal() interprets a non-zero value for current->thread.fault_code as an exception syndrome and displays the message associated with the ESR_ELx.EC field (bits 31:26). current->thread.fault_code is set in compat_arm_syscall() -> arm64_notify_die() with the bad syscall number instead of a valid ESR_ELx value. This means that the ESR_ELx.EC field has the value that the user set for the syscall number and the kernel can end up printing bogus exception messages*. For example, for the syscall number 0x68000000, which evaluates to ESR_ELx.EC value of 0x1A (ESR_ELx_EC_FPAC) the kernel prints this error:

[ 18.349161] syscall[300]: unhandled exception: ERET/ERETAA/ERETAB, ESR 0x68000000, Oops - bad compat syscall(2) in syscall[10000+50000] [ 18.350639] CPU: 2 PID: 300 Comm: syscall Not tainted 5.18.0-rc1 #79 [ 18.351249] Hardware name: Pine64 RockPro64 v2.0 (DT) [..]

which is misleading, as the bad compat syscall has nothing to do with pointer authentication.

Stop arm64_show_signal() from printing exception syndrome information by having compat_arm_syscall() set the ESR_ELx value to 0, as it has no meaning for an invalid system call number. The example above now becomes:

[ 19.935275] syscall[301]: unhandled exception: Oops - bad compat syscall(2) in syscall[10000+50000] [ 19.936124] CPU: 1 PID: 301 Comm: syscall Not tainted 5.18.0-rc1-00005-g7e08006d4102 #80 [ 19.936894] Hardware name: Pine64 RockPro64 v2.0 (DT) [..]

which although shows less information because the syscall number, wrongfully advertised as the ESR value, is missing, it is better than showing plainly wrong information. The syscall number can be easily obtained with strace.

*A 32-bit value above or equal to 0x8000_0000 is interpreted as a negative integer in compat_arm_syscal() and the condition scno < __ARM_NR_COMPAT_END evaluates to true; the syscall will exit to userspace in this case with the ENOSYS error code instead of arm64_notify_die() being called.

Patch / fix

  • Linux Linux 5.4.198, 5.10.121, 5.15.46, 5.17.14, 5.18.3, 5.19
  • linux Debian 14, Debian 13, Debian 12 5.18.5-1

debian advisories DEBIAN-CVE-2022-49520

  • linux Ubuntu 20.04 LTS 5.4.0-126.142
  • linux Ubuntu 22.04 LTS 5.15.0-47.51
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1085.92
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1019.23
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1089.97
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1017.23
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1015.18
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1033.37

ubuntu advisories UBUNTU-CVE-2022-49520

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-284.11.1.el9_2
  • perf RHEL 9 5.14.0-284.11.1.el9_2
  • rtla RHEL 9 5.14.0-284.11.1.el9_2
  • bpftool RHEL 9 7.0.0-284.11.1.el9_2
  • kernel-64k RHEL 9 5.14.0-284.11.1.el9_2
  • kernel-core RHEL 9 5.14.0-284.11.1.el9_2
  • kernel-tools RHEL 9 5.14.0-284.11.1.el9_2
  • python3-perf RHEL 9 5.14.0-284.11.1.el9_2

red hat advisories RHSA-2023:2458

  • kernel-64kb SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS, SLE High Performance Computing 15 SP5-ESPOS 5.14.21-150500.55.100.1
  • kernel-syms SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.100.1
  • kernel-source SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.100.1
  • kernel-default SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +3 more 5.14.21-150500.55.100.1
  • kernel-obs-build SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.100.1
  • kernel-default-base SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.100.1.150500.6.47.1
  • kernel-rt SLE Micro 5.4, SLE Micro 5.3 5.14.21-150400.15.115.1
  • kernel-source-rt SLE Micro 5.4, SLE Micro 5.3 5.14.21-150400.15.115.1

suse advisories SUSE-SU-2025:1241-1SUSE-SU-2025:1183-1SUSE-SU-2025:1176-1SUSE-SU-2025:1027-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2022-49520 updated cvss 5.5

kernel: arm64: compat: Do not treat syscall number as ESR_ELx for a bad syscall

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 9) perf 5.14.0-284.11.1.el9_2, rtla 5.14.0-284.11.1.el9_2, kernel-devel-matched 5.14.0-284.11.1.el9_2, kernel-64k-devel-matched 5.14.0-284.11.1.el9_2, kernel-debug-devel-matched 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.11.1.el9_2, +5 more Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.0.0-284.11.1.el9_2, kernel 5.14.0-284.11.1.el9_2, kernel-64k 5.14.0-284.11.1.el9_2, kernel-core 5.14.0-284.11.1.el9_2, kernel-tools 5.14.0-284.11.1.el9_2, python3-perf 5.14.0-284.11.1.el9_2, +28 more Red Hat Enterprise Linux CRB (v. 9) kernel-debuginfo-common-s390x 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-x86_64 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-aarch64 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-ppc64le 5.14.0-284.11.1.el9_2
    fixed: vendor fix RHSA-2023:2458
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.