VulnerabilityPublished 3 Nov 2026Updated 5 Nov 2026

CVE-2026-120830: libslirp

Affects libslirpSource GCVE Database

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Authoritative record:CVE-2026-120830· High 7.4

Not known to be exploited · CVSS 7.4 High.

Data as of 5 Nov 2026, 12:36 UTC

CVSS 3.1 base score

7.4High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (redhat)	CVSS 3.1	7.4

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

Attack Vector: Adjacent
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: None
Availability: None

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

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 5 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10libslirp`pkg:deb/ubuntu/libslirp?arch=source&distro=stonking`Other threats	Affected =4.9.1-1ubuntu1 =4.9.3-1ubuntu1	Fixed in–
Ubuntu 26.04 LTSlibslirp`pkg:deb/ubuntu/libslirp?arch=source&distro=resolute`Other threats	Affected =4.8.0-1ubuntu1 =4.9.1-1ubuntu1 =4.9.1-1ubuntu1.1	Fixed in–
Ubuntu 24.04 LTSlibslirp`pkg:deb/ubuntu/libslirp?arch=source&distro=noble`Other threats	Affected 4.7.0-1ubuntu1 – 4.7.0-1ubuntu3.1 4 affected builds	Fixed in–
Ubuntu 22.04 LTSlibslirp`pkg:deb/ubuntu/libslirp?arch=source&distro=jammy`Other threats	Affected 4.4.0-1build1 – 4.6.1-1ubuntu0.2 4 affected builds	Fixed in–
Ubuntu 20.04 LTSlibslirp`pkg:deb/ubuntu/libslirp?arch=source&distro=focal`Other threats	Affected 4.0.0-1 – 4.1.0-2ubuntu2.2 8 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Red Hat currently has no practical temporary workaround that fully mitigates this issue. The recommended mitigation is to apply the official security updates once they become available. Until patched, restricting untrusted guests or containers from transmitting network traffic through libslirp virtual network interfaces can reduce the risk by limiting the attack surface. However, this does not fix the underlying vulnerability. The definitive remediation is to upgrade to fixed libslirp builds that clamp the quoted IPv4 payload length to the actual buffer length before copying data into ICMP error responses.

Description

A vulnerability in libslirp's icmp_forward_error() function allows an out-of-bounds heap read when constructing ICMP error responses. The flaw arises because the length of the quoted original IPv4 packet is taken from the IP header without proper clamping to the actual buffer length. This can lead to leakage of host memory into ICMP error packets sent to guests or containers, potentially exposing sensitive information.

Impact

The vulnerability allows an attacker to cause an out-of-bounds heap read, leaking host memory into ICMP error packets sent to guests or containers. This can disclose sensitive information such as cryptographic keys, personally identifiable information, or memory addresses that may aid in bypassing protection mechanisms like ASLR. The flaw does not impact integrity or availability directly but poses a significant confidentiality risk. There are no known exploits in the wild at this time.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Nov 2026, 12:36 UTC

Technical details

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