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NVD / CVE Program· CNA Linux

CVE-2025-21758: ipv6: mcast: add RCU protection to mld_newpack()

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 16.9% (FIRST EPSS); higher than 97% of all records.
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 1b91c597b0214b1b462eb627ec02658c944623f2, 25195f9d5ffcc8079ad743a50c0409dbdc48d98a, 29fa42197f26a97cde29fa8c40beddf44ea5c8f3.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 1b91c597b0214b1b462eb627ec02658c944623f2, 25195f9d5ffcc8079ad743a50c0409dbdc48d98a, 29fa42197f26a97cde29fa8c40beddf44ea5c8f3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: add RCU protection to mld_newpack() mld_newpack() can be called without RTNL or RCU being held. Note that we no longer can use sock_alloc_send_skb() because ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep. Instead use alloc_skb() and charge the net->ipv6.igmp_sk socket under RCU protection.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Feb 27, 2025
Updated
Oct 15, 2026
EPSS
16.9% · 97th percentile
CWE
—

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
5 / 30 · 16.9%

CNA vs NVD score

NVD
5.5
CNA · Linux
7.8
2.3 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-21758

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.26 and later · before 5.15.179
  • linux linux kernel5.16 and later · before 6.1.129
  • linux linux kernel6.2 and later · before 6.6.79
  • linux linux kernel6.7 and later · before 6.12.16
  • linux linux kernel6.13 and later · before 6.13.4
  • linux linux kernel6.14

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.26affected
    • b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 and later · before 29fa42197f26a97cde29fa8c40beddf44ea5c8f3affected · git
    • b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 and later · before e8af3632a7f2da83e27b083f787bced1faba00b1affected · git
    • b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 and later · before 1b91c597b0214b1b462eb627ec02658c944623f2affected · git
    • b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 and later · before 25195f9d5ffcc8079ad743a50c0409dbdc48d98aaffected · git
    • b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 and later · before d60d493b0e65647e0335e6a7c4547abcea7df8e9affected · git
    • b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 and later · before a527750d877fd334de87eef81f1cb5f0f0ca3373affected · git
    • before 2.6.26not affected · semver
    • 5.15.179 and later · up to and including 5.15.*not affected · semver
    • 6.1.129 and later · up to and including 6.1.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.129-16.1.129-1
Debian:13linuxbefore 6.12.16-16.12.16-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-21753Feb 27, 2025 · btrfs: fix use-after-free when attempting to join an aborted transaction
    31Monitor
  • ← EarlierCVE-2025-21756Feb 27, 2025 · vsock: Keep the binding until socket destruction
    31Monitor
  • Later →CVE-2025-21759Feb 27, 2025 · ipv6: mcast: extend RCU protection in igmp6_send()
    33Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux1b91c597b0214b1b462eb627ec02658c944623f2Vendor (CNA)
Linux Linux25195f9d5ffcc8079ad743a50c0409dbdc48d98aVendor (CNA)
Linux Linux29fa42197f26a97cde29fa8c40beddf44ea5c8f3Vendor (CNA)
Linux Linuxa527750d877fd334de87eef81f1cb5f0f0ca3373Vendor (CNA)
Linux Linuxd60d493b0e65647e0335e6a7c4547abcea7df8e9Vendor (CNA)
Linux Linuxe8af3632a7f2da83e27b083f787bced1faba00b1Vendor (CNA)
debian:linux6.1.129-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (10 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records