VulnerabilityPublished 25 Jun 2026Updated 8 Sep 2026

CVE-2026-53249: Linux kernel · ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options

Source GCVE Database

Not known to be exploited · CVSS 5.5 Medium.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.5Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within 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 25 Jun 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-r3wj-w7v3-6mqq

What to do

AI-suggested

A patch has been released that restricts the use of LSRR and SSRR IP options to privileged users with CAP_NET_RAW capability. Applying this patch mitigates the vulnerability. Network administrators should also consider filtering LSRR and SSRR options as recommended by RFC 7126 to reduce exposure.

Description

A vulnerability in the Linux kernel related to IPv4 options LSRR and SSRR has been resolved by restricting their use to users with CAP_NET_RAW capability. This prevents unprivileged applications from exploiting these IP options to route packets through attacker-controlled nodes, which could leak TCP ISN and other protocol information. The vulnerability is mitigated by a patch that enforces this restriction. LSRR and SSRR options are often filtered in many networks but may still be forwarded in some environments. RFC 7126 recommends dropping these options to enhance security.

Impact

Exploitation could allow unprivileged users to manipulate packet routing to leak TCP ISN and other protocol information, potentially aiding in reconnaissance or further attacks. The vulnerability does not impact confidentiality or integrity directly but affects availability (as per CVSS vector) and could facilitate indirect attacks.

Summary

The Linux kernel vulnerability CVE-2026-53249 involves the Loose Source and Record Route (LSRR) and Strict Source and Record Route (SSRR) IPv4 options. Previously, unprivileged users could set these options, potentially allowing packets to be routed through attacker-controlled nodes, leading to leakage of TCP Initial Sequence Numbers (ISN) and possibly other protocol data. The patch restricts setting these IP options to users with the CAP_NET_RAW capability, thereby preventing unprivileged exploitation. This aligns with RFC 7126 recommendations to filter such IPv4 options.

References

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