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CVE-2026-93259
powerpc/irq: Fix missing r2 clobber in PCREL inline assembly
Overview
Description

In the Linux kernel, the following vulnerability has been resolved: powerpc/irq: Fix missing r2 clobber in PCREL inline assembly In CONFIG_PPC_KERNEL_PCREL mode, r2 is no longer reserved for the TOC pointer and is available as a caller-saved register [0]. Both call_do_irq() and call_do_softirq() use inline assembly to call functions with stack switching, but fail to list r2 in their clobber lists. This causes the compiler to assume r2 is preserved across these calls, leading to register corruption when the called functions (__do_irq and __do_softirq) clobber r2. As a result of this kernel crash during interrupt handling is seen and the kernel fails to boot: BUG: Unable to handle kernel data access on write at 0xc000000404697638 Faulting instruction address: 0xc0000000000181ec Oops: Kernel access of bad area, sig: 11 [#1] NIP [c0000000000181ec] __do_IRQ+0x6c/0xc0 With older GCC, the compiler would conservatively allocate callee-saved registers (like r31) for values spanning function calls, accidentally avoiding the bug: <__do_IRQ>: 00 00 00 60 nop a6 02 08 7c mflr r0 f8 ff e1 fb std r31,-8(r1) f0 ff c1 fb std r30,-16(r1) 2d 03 10 06 pla r31,53297316 ... 3d e8 ff 4b bl c0000000000165ac <__do_irq> 00 00 21 e8 ld r1,0(r1) 28 00 4d e9 ld r10,40(r13) 40 00 21 38 addi r1,r1,64 2a f9 aa 7f stdx r29,r10,r31 With newer GCC 14, the compiler uses r2 for such values, exposing the missing clobber specification: <__do_IRQ>: 00 00 00 60 nop a6 02 08 7c mflr r0 f0 ff c1 fb std r30,-16(r1) f8 ff e1 fb std r31,-8(r1) 29 02 10 06 pla r2,36252592 # c0000000022aadc0 <__irq_regs> ... 85 dc ff 4b bl c000000000015ee0 <__do_irq> 00 00 21 e8 ld r1,0(r1) 28 00 2d e9 ld r9,40(r13) 30 00 21 38 addi r1,r1,48 2a 11 c9 7f stdx r30,r9,r2 Fix this by adding r2 to the clobber list for both call_do_irq() and call_do_softirq() when CONFIG_PPC_KERNEL_PCREL is enabled. [0]: https://www.mail-archive.com/[email protected]/msg313226.html

Details
INFO

Published Date :

Sept. 24, 2026, 4:17 p.m.

Last Modified :

Sept. 24, 2026, 4:17 p.m.

Remotely Exploit :

No

Source :

416baaa9-dc9f-4396-8d5f-8c081fb06d67
Impact
Affected Products

The following products are affected by CVE-2026-93259 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Linux linux_kernel
: Total Affected Vendor : 1 | Products : 1
Solution
Update the Linux kernel to include the r2 register in inline assembly clobber lists.
  • Add r2 to the clobber list in call_do_irq.
  • Add r2 to the clobber list in call_do_softirq.
  • Ensure CONFIG_PPC_KERNEL_PCREL is configured correctly.
  • Apply the provided kernel patch.
References
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-93259.

URL Resource
https://git.kernel.org/stable/c/00be69070d91d2be978e752bb117a0a4db0e1281
https://git.kernel.org/stable/c/602ee44415f3eaa7893f7fc488c7c1d4a0bdbd7a
https://git.kernel.org/stable/c/7b0093b638c8f2b94b0778a69fd1ccad54299b29
https://git.kernel.org/stable/c/90d953002cf0b233dd053a0e7cb67ab79cebd0e3
https://git.kernel.org/stable/c/dcc442a49c0f540193910dacdca7506bcadc7ec5
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-93259 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-93259 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-93259 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-93259 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    Sep. 24, 2026

    Action Type Old Value New Value
    Added Description In the Linux kernel, the following vulnerability has been resolved: powerpc/irq: Fix missing r2 clobber in PCREL inline assembly In CONFIG_PPC_KERNEL_PCREL mode, r2 is no longer reserved for the TOC pointer and is available as a caller-saved register [0]. Both call_do_irq() and call_do_softirq() use inline assembly to call functions with stack switching, but fail to list r2 in their clobber lists. This causes the compiler to assume r2 is preserved across these calls, leading to register corruption when the called functions (__do_irq and __do_softirq) clobber r2. As a result of this kernel crash during interrupt handling is seen and the kernel fails to boot: BUG: Unable to handle kernel data access on write at 0xc000000404697638 Faulting instruction address: 0xc0000000000181ec Oops: Kernel access of bad area, sig: 11 [#1] NIP [c0000000000181ec] __do_IRQ+0x6c/0xc0 With older GCC, the compiler would conservatively allocate callee-saved registers (like r31) for values spanning function calls, accidentally avoiding the bug: <__do_IRQ>: 00 00 00 60 nop a6 02 08 7c mflr r0 f8 ff e1 fb std r31,-8(r1) f0 ff c1 fb std r30,-16(r1) 2d 03 10 06 pla r31,53297316 ... 3d e8 ff 4b bl c0000000000165ac <__do_irq> 00 00 21 e8 ld r1,0(r1) 28 00 4d e9 ld r10,40(r13) 40 00 21 38 addi r1,r1,64 2a f9 aa 7f stdx r29,r10,r31 With newer GCC 14, the compiler uses r2 for such values, exposing the missing clobber specification: <__do_IRQ>: 00 00 00 60 nop a6 02 08 7c mflr r0 f0 ff c1 fb std r30,-16(r1) f8 ff e1 fb std r31,-8(r1) 29 02 10 06 pla r2,36252592 # c0000000022aadc0 <__irq_regs> ... 85 dc ff 4b bl c000000000015ee0 <__do_irq> 00 00 21 e8 ld r1,0(r1) 28 00 2d e9 ld r9,40(r13) 30 00 21 38 addi r1,r1,48 2a 11 c9 7f stdx r30,r9,r2 Fix this by adding r2 to the clobber list for both call_do_irq() and call_do_softirq() when CONFIG_PPC_KERNEL_PCREL is enabled. [0]: https://www.mail-archive.com/[email protected]/msg313226.html
    Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/93xxx/CVE-2026-93259.json">CVE-2026-93259</a>
    Added Reference https://git.kernel.org/stable/c/00be69070d91d2be978e752bb117a0a4db0e1281
    Added Reference https://git.kernel.org/stable/c/602ee44415f3eaa7893f7fc488c7c1d4a0bdbd7a
    Added Reference https://git.kernel.org/stable/c/7b0093b638c8f2b94b0778a69fd1ccad54299b29
    Added Reference https://git.kernel.org/stable/c/90d953002cf0b233dd053a0e7cb67ab79cebd0e3
    Added Reference https://git.kernel.org/stable/c/dcc442a49c0f540193910dacdca7506bcadc7ec5
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CVSS
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