CVE-2026-31521

Home/CVE/In the Linux kernel, the following vulnerability has been resolved: module: Fix kernel panic when a symbol st_shndx is

CVE

In the Linux kernel, the following vulnerability has been resolved: module: Fix kernel panic when a symbol st_shndx is

In the Linux kernel, the following vulnerability has been resolved: module: Fix kernel panic when a symbol st_shndx is out of bounds The module loader doesn't check for bounds of the ELF section index in simplify_symbols(): for (i = 1.

i < symsec-sh_size / sizeof(Elf_Sym)

i++) { const char name = info-strtab + sym[i].st_name; switch (sym[i].st_shndx) { case SHN_COMMON: [...] default: / Divert to percpu allocation if a percpu var. */ if (sym[i].st_shndx == info-index.pcpu) secbase = (unsigned long)mod_percpu(mod); else / HERE -- / secbase = info-sechdrs[sym[i].st_shndx].sh_addr; sym[i].st_value += secbase; break; } A symbol with an out-of-bounds st_shndx value, for example 0xffff (known as SHN_XINDEX or SHN_HIRESERVE), may cause a kernel panic: BUG: unable to handle page fault for address: ... RIP: 0010:simplify_symbols+0x2b2/0x480 ... Kernel panic - not syncing: Fatal exception This can happen when module ELF is legitimately using SHN_XINDEX or when it is corrupted. Add a bounds check in simplify_symbols() to validate that st_shndx is within the valid range before using it. This issue was discovered due to a bug in llvm-objcopy, see relevant discussion for details [1]. [1] https://lore.kernel.org/linux-modules/[email protected]/.

MEDIUM · CVSS 5.5 EPSS 0.00014

Monitor

No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence

Sigma rules0 YARA rules0

Look this up elsewhere - one-click external pivots

NVD CVE.org CISA Vulners Exploit-DB GitHub PoC VulnCheck KEV GreyNoise

▸ How to read a CVE - triage first, then detect and patch

This page is every public fact about CVE-2026-31521, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.

Triage: should I act now? Four signals, and they are not interchangeable:

CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked. EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal. CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score. Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.

How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.

Then what - two workflows:

Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits. PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.

Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).

View attack path from CVE-2026-31521

◆

ATT&CK techniques

Techniques this CVE enables - linked via CWECAPECATT&CK. High◆ = named directly in ATT&CK or Nuclei templates.

T1068 · Exploitation for Privilege Escalation

▤ Build a SIEM detection for these techniques

⬡

Weakness Classification

CWE-787Out-of-bounds Write

▤

Affected Products & Versions

linux kernel>= 2.6.12.1 and < 5.15.203
linux kernel>= 5.16 and < 6.1.168
linux kernel>= 6.2 and < 6.6.131
linux kernel>= 6.7 and < 6.12.80
linux kernel>= 6.13 and < 6.18.21
linux kernel>= 6.19 and < 6.19.11
linux kernelall versions

▣

Scoring & Timeline

5.5

MEDIUM · CVSS v3.1 · 416baaa9-dc9f-4396-8d5f-8c081fb06d67

View on NVD

Attack Vector

Network Adjacent Local Physical

Attack Complexity

Low High

Privileges Required

None Low High

User Interaction

None Required

Scope

Unchanged Changed

Confidentiality

None Low High

Integrity

None Low High

Availability

None Low High

Published to NVD22 Apr 2026 · 02:16 PM

CVSS VectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

⚑

Vendor Advisories

suse-csafopenSUSE-SU-2026:20912-1
suse-csafSUSE-SU-2026:22048-1
msrcCVE-2026-31521

🔗

References & Sources

Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.

https://git.kernel.org/stable/c/082f15d2887329e0f43fd3727e69365f5bfe5d2cPatch

https://git.kernel.org/stable/c/4bbdb0e48176fd281c2b9a211b110db6fd94e175Patch

https://git.kernel.org/stable/c/5d16f519b6eb1d071807e57efe0df2baa8d32ad6Patch

https://git.kernel.org/stable/c/6ba6957c640f58dc8ef046981a045da43e47ea23Patch

https://git.kernel.org/stable/c/ec2b22a58073f80739013588af448ff6e2ab906fPatch

https://git.kernel.org/stable/c/ef75dc1401d8e797ee51559a0dd0336c225e1776Patch

Show all 7 references

https://git.kernel.org/stable/c/f9d69d5e7bde2295eb7488a56f094ac8f5383b92Patch