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CVE-2026-53110
s390/bpf: Zero-extend bpf prog return values and kfunc arguments
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem arch/s390. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53110 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
s390x ABI requires callers to zero-extend unsigned arguments and sign-extend signed arguments, and callees to zero-extend unsigned return values and sign-extend signed return values. s390 BPF JIT currently implements only sign extension. Fix this omission and implement zero extension too.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
arch/s390/net/bpf_jit_comp.c
- What this is
- BPF JIT for S390MAINTAINERS section matched on arch/s390/net/ · bpf@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_BPF_JIT /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormy
- trixie, forky, sidYnot built on s390x/s390x
- y
- built into the kernel image on every flavour - only a patch removes it
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_BPF_JIT
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-06-24 (4 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- arch/s390
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.3 | 6.6.141 | edc90a12073b |
| 6.3 | 6.12.91 | 44c4f999b03f |
| 6.3 | 6.18.33 | 366b0e05ee24 |
| 6.3 | 7.0.10 | 834918a77be5 |
| 6.3 | 7.1 | 202e42e4aa89 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The vulnerable code is reached by locally loading or attaching BPF programs through the bpf() syscall and then executing the JITed program or generated trampoline. It is not directly reachable from remote network packets without prior local BPF program installation.
- AC:LAttack complexity, low
- An attacker can craft BPF bytecode/attachments that exercise unsigned kfunc arguments or trampoline return values, and there is no race or external timing condition required. The bug is a deterministic ABI/JIT miscompilation on affected s390 systems.
- PR:LPrivileges required, low
- Loading kfunc/tracing BPF normally requires BPF-related capabilities, but BPF token delegation can evaluate these in a non-init user namespace in delegated/containerized deployments. Following the higher-severity rule, this is scored as low privileges rather than requiring real init-namespace root.
- UI:NUser interaction, none
- No victim action is needed after the attacker can issue the relevant bpf() syscalls. The attacker loads/attaches and triggers the affected BPF program path directly.
- S:UScope, unchanged
- The vulnerability affects kernel execution in the same security authority as the vulnerable component. It is a local kernel compromise/DoS style issue, not a VM escape or separate security-scope boundary bypass.
- C:HConfidentiality impact, high
- The missing zero-extension lets attacker-controlled high bits cross the verifier/native ABI boundary for kfunc calls and trampoline returns. This can plausibly turn verifier-assumed bounded values into unsafe kernel values, matching prior BPF JIT verifier-bypass classes with kernel memory disclosure potential.
- I:HIntegrity impact, high
- Incorrect unsigned argument or return extension can corrupt kernel control/data flow through kfuncs or BPF modify-return trampolines. Under the required higher-severity assumption, this is treated as exploitable for kernel memory modification or privilege escalation.
- A:HAvailability impact, high
- At minimum, passing ABI-invalid kfunc arguments or malformed trampoline return values can trigger kernel oops/panic paths, as similar BPF JIT argument-extension bugs have done. The attacker can repeatedly load/trigger the crafted BPF program.