VulnerabilityPublished 19 Jul 2026

CVE-2026-63919: Linux kernel · xfrm: input: hold netns during deferred transport reinjection

Source GCVE Database

Authoritative record:CVE-2026-63919· High 8.8

Not known to be exploited · CVSS 8.8 High · fixed in c16f74dc1d75d0e2e7670076d5375deda110ebeb : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

8.8High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in c16f74dc1d75d0e2e7670076d5375deda110ebeb, 55ddfc41451f01c588089cd74957a05311b6f202, 48ce101cd630d6745b6923b5bad8358bc4c119da +5

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-c9j4-h9xp-p2mj

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 7b3801927e52f8621de311277f7fc727635019e7, < c16f74dc1d75d0e2e7670076d5375deda110ebeb	Fixed in c16f74dc1d75d0e2e7670076d5375deda110ebeb
LinuxLinux	Affected ≥ 7b3801927e52f8621de311277f7fc727635019e7, < 55ddfc41451f01c588089cd74957a05311b6f202	Fixed in 55ddfc41451f01c588089cd74957a05311b6f202
LinuxLinux	Affected ≥ 7b3801927e52f8621de311277f7fc727635019e7, < 48ce101cd630d6745b6923b5bad8358bc4c119da	Fixed in 48ce101cd630d6745b6923b5bad8358bc4c119da
LinuxLinux	Affected ≥ 7b3801927e52f8621de311277f7fc727635019e7, < 9f67a36e91bb50d358760f381f233913fe5c09f8	Fixed in 9f67a36e91bb50d358760f381f233913fe5c09f8
LinuxLinux	Affected ≥ 7b3801927e52f8621de311277f7fc727635019e7, < 9f7ebb45a83afc3216e855e57d51bb4bc9b5232e	Fixed in 9f7ebb45a83afc3216e855e57d51bb4bc9b5232e
LinuxLinux	Affected ≥ 7b3801927e52f8621de311277f7fc727635019e7, < 8dfabcba6a943a7a02ebe1e1637c361ba96acbaa	Fixed in 8dfabcba6a943a7a02ebe1e1637c361ba96acbaa

AI-suggested

A fix has been implemented in the Linux kernel to properly manage the network namespace reference during deferred transport reinjection. Users should apply the official kernel updates that include this fix once available. Patch status is not explicitly confirmed in the provided data; check the vendor or kernel mailing list advisories for the current remediation status and updated kernel versions containing the fix.

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: input: hold netns during deferred transport reinjection Transport-mode reinjection stores a struct net pointer in skb->cb and uses it later from xfrm_trans_reinject(). That pointer must stay valid until the deferred callback runs. Take a netns reference when queueing deferred reinjection work and drop it after the callback completes. Use maybe_get_net() so the queueing path does not revive a namespace that is already being torn down. This keeps the existing workqueue design and fixes the netns lifetime handling in one place for all users of xfrm_trans_queue_net().

Impact

Improper handling of the network namespace pointer could lead to use-after-free or invalid memory access within the kernel during deferred transport-mode reinjection processing. This could cause kernel instability or crashes. No known exploits are reported in the wild. The vulnerability affects the Linux kernel's xfrm subsystem but no specific affected versions are stated.

Summary

The Linux kernel's xfrm input code for transport-mode reinjection previously stored a struct net pointer in skb->cb for later use in xfrm_trans_reinject(). This pointer needed to remain valid until the deferred callback executed. The vulnerability stemmed from improper lifetime management of the network namespace pointer, risking use of an invalid pointer if the namespace was torn down before the callback. The fix introduced taking a netns reference via maybe_get_net() when queueing deferred reinjection work and dropping it after the callback finishes, ensuring the pointer remains valid and preventing potential kernel memory corruption or crashes related to network namespace lifecycle mismanagement.

References

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