CVE-2025-39797

Packet drops via duplicate inbound security parameter indexes

Published Sep 12, 2025 · Updated Sep 12, 2025

Improper SPI allocation in the Linux kernel XFRM subsystem allows local users to cause IPsec packet drops through duplicate inbound SAs. xfrm_alloc_spi() checks a destination-dependent hash bucket and returns success when the same SPI exists under a different destination, allowing ambiguous inbound lookups. Reliable triggering requires a narrowed StrongSwan SPI range and more child SAs than available values; collisions are rare with the default range.

CVSS severity7.8
High
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper SPI allocation in the Linux kernel XFRM subsystem allows local users to cause IPsec packet drops through duplicate inbound SAs. xfrm_alloc_spi() checks a destination-dependent hash bucket and returns success when the same SPI exists under a different destination, allowing ambiguous inbound lookups. Reliable triggering requires a narrowed StrongSwan SPI range and more child SAs than available values; collisions are rare with the default range.

The record

CVE
CVE-2025-39797
Published
Sep 12, 2025
Updated
Sep 12, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 12, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <29e9158f91f99057dbd35db5e8674d93b38549fe
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2fc5b54368a1bf1d2d74b4d3b8eea5309a653e38
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3d8090bb53424432fa788fe9a49e8ceca74f0544
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <94f39804d891cffe4ce17737d295f3b195bc7299
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c67d4e7a8f90fb6361ca89d4d5c9a28f4e935e47

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <29e9158f91f99057dbd35db5e8674d93b38549fe; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2fc5b54368a1bf1d2d74b4d3b8eea5309a653e38; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3d8090bb53424432fa788fe9a49e8ceca74f0544; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <94f39804d891cffe4ce17737d295f3b195bc7299; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c67d4e7a8f90fb6361ca89d4d5c9a28f4e935e47

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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