Linux KernelOperating system · Linux

CVE-2025-21949

MEDIUM · 5.5 CVSS v3.1 Published 2025-04-01

Fix available

A fix is available. Upgrade to 6.13.7 or later.

See remediation →

57/100

Remediation priority · Elevated

Zero-click Patch available

Official description

NVD · unedited

In the Linux kernel, the following vulnerability has been resolved: LoongArch: Set hugetlb mmap base address aligned with pmd size With ltp test case "testcases/bin/hugefork02", there is a dmesg error report message such as: kernel BUG at mm/hugetlb.c:5550! Oops - BUG[#1]: CPU: 0 UID: 0 PID: 1517 Comm: hugefork02 Not tainted 6.14.0-rc2+ #241 Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 2/2/2022 pc 90000000004eaf1c ra 9000000000485538 tp 900000010edbc000 sp 900000010edbf940 a0 900000010edbfb00 a1 9000000108d20280 a2 00007fffe9474000 a3 00007ffff3474000 a4 0000000000000000 a5 0000000000000003 a6 00000000003cadd3 a7 0000000000000000 t0 0000000001ffffff t1 0000000001474000 t2 900000010ecd7900 t3 00007fffe9474000 t4 00007fffe9474000 t5 0000000000000040 t6 900000010edbfb00 t7 0000000000000001 t8 0000000000000005 u0 90000000004849d0 s9 900000010edbfa00 s0 9000000108d20280 s1 00007fffe9474000 s2 0000000002000000 s3 9000000108d20280 s4 9000000002b38b10 s5 900000010edbfb00 s6 00007ffff3474000 s7 0000000000000406 s8 900000010edbfa08 ra: 9000000000485538 unmap_vmas+0x130/0x218 ERA: 90000000004eaf1c __unmap_hugepage_range+0x6f4/0x7d0 PRMD: 00000004 (PPLV0 +PIE -PWE) EUEN: 00000007 (+FPE +SXE +ASXE -BTE) ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7) ESTAT: 000c0000 [BRK] (IS= ECode=12 EsubCode=0) PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) Process hugefork02 (pid: 1517, threadinfo=00000000a670eaf4, task=000000007a95fc64) Call Trace: [<90000000004eaf1c>] __unmap_hugepage_range+0x6f4/0x7d0 [<9000000000485534>] unmap_vmas+0x12c/0x218 [<9000000000494068>] exit_mmap+0xe0/0x308 [<900000000025fdc4>] mmput+0x74/0x180 [<900000000026a284>] do_exit+0x294/0x898 [<900000000026aa30>] do_group_exit+0x30/0x98 [<900000000027bed4>] get_signal+0x83c/0x868 [<90000000002457b4>] arch_do_signal_or_restart+0x54/0xfa0 [<90000000015795e8>] irqentry_exit_to_user_mode+0xb8/0x138 [<90000000002572d0>] tlb_do_page_fault_1+0x114/0x1b4 The problem is that base address allocated from hugetlbfs is not aligned with pmd size. Here add a checking for hugetlbfs and align base address with pmd size. After this patch the test case "testcases/bin/hugefork02" passes to run. This is similar to the commit 7f24cbc9c4d42db8a3c8484d1 ("mm/mmap: teach generic_get_unmapped_area{_topdown} to handle hugetlb mappings").

Technical summary

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions

NVD · CPE data

Linux KernelOperating system

Affected:>= 5.19, < 6.13.7= 6.14

CVSS breakdown

From the vector

Attack vector: Local
Complexity: Low
Privileges: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

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

Remediation

dbcve · scoped

Upgrade available Upgrade to 6.13.7 or later

Fixed in 6.13.7

Vendor patch git.kernel.org →

Recommended fix High confidence

Linux kernel 6.13.7+ or 6.14.1+ (or any stable release > 6.14)

1. Identify the current running kernel version using 'uname -r' or 'cat /proc/version'
2. Check if the system is running a LoongArch architecture kernel (affected arch: LoongArch)
3. Upgrade the Linux kernel to version 6.13.7 or later, or version 6.14.1 or later
4. If using a distribution kernel, upgrade to the distribution's kernel package that includes the fix (e.g., for stable/lts distributions)
5. Reboot the system to load the fixed kernel
6. Verify the kernel version after reboot with 'uname -r' to confirm the fix is applied
7. Re-run the ltp test case 'testcases/bin/hugefork02' to verify the vulnerability is fixed

Caveat Kernel upgrades may require reboot and could have driver/feature changes; verify compatibility with LoongArch hardware and any custom modules before upgrading in production

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References

Primary sources

git.kernel.orgPatch / commit
git.kernel.orgPatch
git.kernel.orgPatch
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-21949 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2025-21949?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

A fix existsUpgrade to 6.13.7 or later

Severity 5.5 Medium

Exploit likelihood EPSS, next 30 days 0.2%

Affects: Linux Kernel

Remediation

Need this fixed?

Get a fix

Estimated effortfrom ~9 hrs

ComplexityModerate

Typical engagementfrom $1,600

What a fix involves

We scope it with you and confirm a fixed quote
A specialist builds a reviewed fix
You deploy it to staging first
Optional re-test once it’s live

We specialise in CVE remediation. Send your environment and we’ll scope CVE-2025-21949 and return a fixed quote.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Remediation

References