VulnerabilityPublished 23 Oct 2026Updated 24 Oct 2026

CVE-2026-99030: Linux kernel · net: skbuff: don't leave stale bytes in skb_copy_and_csum_bits()

Source GCVE Database

Authoritative record:CVE-2026-99030· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in ab9414ed70bd783e902a85c350620dee269bcb2b : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in ab9414ed70bd783e902a85c350620dee269bcb2b, 5551399751e2c9f31e4f3428040985a07e79d9c2, 39d1a6b601831237c6038b5e3ac8dbb883c1700a +1

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

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

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: 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: 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: 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 23 Oct 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-2m74-g73v-pv5c

What to do

Upgrade Linux kernel to ab9414ed70bd783e902a85c350620dee269bcb2b, 5551399751e2c9f31e4f3428040985a07e79d9c2, 39d1a6b601831237c6038b5e3ac8dbb883c1700a or 5f19b9cfff79508e8cb09be40d014cb0807f3854.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 65249feb6b3df9e17bab5911ee56fa7b0971e231, < ab9414ed70bd783e902a85c350620dee269bcb2b	Fixed in ab9414ed70bd783e902a85c350620dee269bcb2b
LinuxLinux	Affected ≥ 65249feb6b3df9e17bab5911ee56fa7b0971e231, < 5551399751e2c9f31e4f3428040985a07e79d9c2	Fixed in 5551399751e2c9f31e4f3428040985a07e79d9c2
LinuxLinux	Affected ≥ 65249feb6b3df9e17bab5911ee56fa7b0971e231, < 39d1a6b601831237c6038b5e3ac8dbb883c1700a	Fixed in 39d1a6b601831237c6038b5e3ac8dbb883c1700a
LinuxLinux	Affected ≥ 65249feb6b3df9e17bab5911ee56fa7b0971e231, < 5f19b9cfff79508e8cb09be40d014cb0807f3854	Fixed in 5f19b9cfff79508e8cb09be40d014cb0807f3854
LinuxLinux	Affected =6.12	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: don't leave stale bytes in skb_copy_and_csum_bits() When skb_copy_and_csum_bits() reaches unreadable frags it returns 0 after copying only the linear part, and the rest of the caller's buffer is left as it was. The callers copy into a buffer that is about to go out on the wire: an ICMP error quoting the offending packet, or a driver's TX bounce buffer in skb_copy_and_csum_dev(). Neither buffer is zeroed beforehand, so whatever was in memory there gets sent. Zero the part of the buffer we didn't fill. The checksum usually won't match the data any more, so the receiver will usually drop the packet, but either way it no longer carries anything it shouldn't. Only zero for a positive @len, a negative one from a broken caller must not turn into a huge memset().

References

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