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NVD / CVE Program· CNA Linux

CVE-2025-21864: tcp: drop secpath at the same time as we currently drop dst

Noroxi assessment

Priority: Monitor (action score 22/100)

  • 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: 0.27% (FIRST EPSS).
  • 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 69cafd9413084cd5012cf5d7c7ec6f3d493726d9, 87858bbf21da239ace300d61dd209907995c0491, 9b6412e6979f6f9e0632075f8f008937b5cd4efd; azl3 kernel 6.6.78.1-3 on Azure Linux 3.0 6.6.82.1-1; azl3 kernel 6.6.82.1-1 on Azure Linux 3.0 6.6.82.1-1.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 69cafd9413084cd5012cf5d7c7ec6f3d493726d9, 87858bbf21da239ace300d61dd209907995c0491, 9b6412e6979f6f9e0632075f8f008937b5cd4efd; azl3 kernel 6.6.78.1-3 on Azure Linux 3.0 6.6.82.1-1; azl3 kernel 6.6.82.1-1 on Azure Linux 3.0 6.6.82.1-1 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: tcp: drop secpath at the same time as we currently drop dst Xiumei reported hitting the WARN in xfrm6_tunnel_net_exit while running tests that boil down to: - create a pair of netns - run a basic TCP test over ipcomp6 - delete the pair of netns The xfrm_state found on spi_byaddr was not deleted at the time we delete the netns, because we still have a reference on it. This lingering reference comes from a secpath (which holds a ref on the xfrm_state), which is still attached to an skb. This skb is not leaked, it ends up on sk_receive_queue and then gets defer-free'd by skb_attempt_defer_free. The problem happens when we defer freeing an skb (push it on one CPU's defer_list), and don't flush that list before the netns is deleted. In that case, we still have a reference on the xfrm_state that we don't expect at this point. We already drop the skb's dst in the TCP receive path when it's no longer needed, so let's also drop the secpath. At this point, tcp_filter has already called into the LSM hooks that may require the secpath, so it should not be needed anymore. However, in some of those places, the MPTCP extension has just been attached to the skb, so we cannot simply drop all extensions.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Mar 12, 2025
Updated
Oct 15, 2026
EPSS
0.2% · 20th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

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

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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 kernel5.19 and later · before 6.1.130
  • linux linux kernel6.2 and later · before 6.6.80
  • linux linux kernel6.7 and later · before 6.12.17
  • linux linux kernel6.13 and later · before 6.13.5
  • 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

    • 5.19affected
    • 68822bdf76f10c3dc80609d4e2cdc1e847429086 and later · before 87858bbf21da239ace300d61dd209907995c0491affected · git
    • 68822bdf76f10c3dc80609d4e2cdc1e847429086 and later · before f1d5e6a5e468308af7759cf5276779d3155c5e98affected · git
    • 68822bdf76f10c3dc80609d4e2cdc1e847429086 and later · before cd34a07f744451e2ecf9005bb7d24d0b2fb83656affected · git
    • 68822bdf76f10c3dc80609d4e2cdc1e847429086 and later · before 69cafd9413084cd5012cf5d7c7ec6f3d493726d9affected · git
    • 68822bdf76f10c3dc80609d4e2cdc1e847429086 and later · before 9b6412e6979f6f9e0632075f8f008937b5cd4efdaffected · git
    • before 5.19not affected · semver
    • 6.1.130 and later · up to and including 6.1.*not affected · semver
    • 6.6.80 and later · up to and including 6.6.*not affected · semver
    • 6.12.17 and later · up to and including 6.12.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.133-16.1.133-1
Debian:13linuxbefore 6.12.17-16.12.17-1

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-2025-21862Mar 12, 2025 · drop_monitor: fix incorrect initialization order
    22Monitor
  • ← EarlierCVE-2025-21863Mar 12, 2025 · io_uring: prevent opcode speculation
    31Monitor
  • Later →CVE-2025-21865Mar 12, 2025 · gtp: Suppress list corruption splat in gtp_net_exit_batch_rtnl().
    22Monitor

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 Linux69cafd9413084cd5012cf5d7c7ec6f3d493726d9Vendor (CNA)
Linux Linux87858bbf21da239ace300d61dd209907995c0491Vendor (CNA)
Linux Linux9b6412e6979f6f9e0632075f8f008937b5cd4efdVendor (CNA)
Linux Linuxcd34a07f744451e2ecf9005bb7d24d0b2fb83656Vendor (CNA)
Linux Linuxf1d5e6a5e468308af7759cf5276779d3155c5e98Vendor (CNA)
azl3 kernel 6.6.78.1-3 on Azure Linux 3.06.6.82.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 kernel 6.6.82.1-1 on Azure Linux 3.06.6.82.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.133-1 · 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.

No history yet (it accumulates with the daily EPSS job).

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)

CWE-476 · NULL Pointer Dereference

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✗ → ✓

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References

Show all references (9 more)

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

All records